Why not both? I mean, you can't have too many websites on mesothelioma, can you? Just be sure to jiggle your content around so you don't get hit with a duplicate content penalty.

This is a little OT, but having keywords in the URL can really help with se placement.
I started with one site and have changed my topic a little and came out with a lot of small sites and increased my income by a lot.

should it be wise to create one website with all different topics like weight loss, diabetes, hypertension, or to create a separate website for each major topis from Adsense standpoint and from traffic standpoint.

That would depend on the type of website you are planning to create.

Are you going to build a health site that covers general information or planning on building an authority site. If you are going to build a general information site I would use one site. If it is going to be an authority site I would use several sites covering the different topics.

Here is my opinion on what the difference is. Take diabetes for instance. In a general site you would talk about what it is and a little background behind it. On an authority site you could cover every aspect of diabetes. This would include things like:
-what it is,
-different types of diabetes
-what drugs or treatments are available now and which ones are in the pipeline,
-information about clinical trials
-are genetics involved in contacting it
-are people in certain countries more likely to get it
-information about support groups
.....

I am a Doc, and wanted to start a health-related website, but someone suggested that in Adsense making small topic-related websites (one for each major topic) will pay more and get more visitors.

Thanks for the help and suggestions.

I suspect most of the benefits will come from having multiple pages - each on very specific aspects of your subjects. I'm not sure that multiple domains will necessarily add much.

Also, health is a very competitive subject area, so you'll need to have a "unique selling proposition" (or, better yet, unique content) if you hope to get inbound links and traffic.

You might want to consider, given that you are a doctor, is how much you want to build your personal reputation, and how much that reputation can eventually provide you with traffic.

You are not going to build your personal "expert" reputation by having 20 different sites, each discussing one specific area. Those 20 different sites might serve you well to start off, but they are not likely to compare favorable to a site based on *your* authority in the long run.

To use one of our own as an example, europeforvisitors would probably not be to the point he is now, if he just built lots of sites covering each of the major cities in Europe.

When he writes an article about something in a city that he has not covered before, he doesn't have to put up a new site get links, and include a lot of garbage filler content. He just puts it up and tweaks his navigation a little bit.

I'm not advocating for a single site, just suggesting that it is not so clear cut when looking at all the possiblities.

But I think what is clear, is that you should have separate pages for separate topics and subtopics in order to maximise and Adsense income.

BigDave writes a lot of sense and personally, as an owner of 100+ sites all devoted to the same subject matter, I have two core sites covering the general aspects of my specialised construction products and all my satellite sites are much more in-depth by country or specific product.

I can assure you that the two generalised core sites easily earn more overall (70%) than the satellite sites however the satellites do have a far higher CTR and eCPM.

One benefit of having several sites is that one is less likely to get dumped by one of the dreaded Google algo updates.

If you ensure you have a solid directory structure when you construct your first general site then there would be no difficulty in constructing a more specialised satellite site later on and linking directly to it.

I would definitely start with a general site and if some tasty keyword domain names became available then consider spreading out later on.

I have tried both. Logic tells me the more specific should perform better re adsense. However, the actual findings were different. I find the more generalized pages serve better performing ads. Doesn't make sense to me, and I am sure that the more specific sites will eventually out-perform. I guess, like most things here everyone has different experiences and different results. I would try the more the general, then perhaps fine tune it to perhaps the more specialised areas that are performing well.

Having been through a Google disaster, with its 70% hit to earnings for about 5 weeks, I would NEVER take the risk of having all my work residing in one domain.

In my case, when the bad times came, I lost almost all traffic to one domain, and lived off the earnings from several others. It taught me a lesson I'll never forget. Everything came back eventually, so I am doing fine now.

As for how topics and domains are related, I doubt that it matters much. I reach the same health based market from multiple domains. Whats more important, IMHO, is to build solid sections (groups of pages in their own directory) that deliver thoroughly on one topic. You'll find these generate revenue and gain rankings very much the same as a seperate domain.

Optirex gave good advice above.

Humble request for suggestions.

Here are some relevant questions for you:

• Where are you going to get traffic? Are you counting on free SE traffic (which gets harder to get every single day)?
  
• Do you have a bunch of top-10 health authority sites just waiting to link to you, or are you going to be starting on square less-than-zero, just hoping folks will link to you?
  
• Where are you going to get content? If you're planning to write it all yourself, how did you figure you would achieve any kind of authority status any time soon for something as broad and competitive as the health field?
  

Webmasters tend to put way more emphasis on how content is divided among domains than search engines do. Search engines see link structure and content and give that much more emphasis than domain structure. You can pick a single domain with an abstract name and start trying to build content there that is narrowly focussed. That lets you delay the decision you think you're facing now: you can later either broaden the content of the site are start a new one with a different focus.

It could be that you have a staff of a dozen expert writers and a budget of $1 million behind you, in which case your question is well worth pondering at this time. Or it could be that you're setting out by your lonesome to tap some of that easy AdSense money everybody's talking about, in which case your question is somewhat irrelevant -- you'll have such a different perspective after gaining some altitude on the learning curve that you'll laugh at whatever decision you make now.

I have tried both. Logic tells me the more specific should perform better re adsense. However, the actual findings were different. I find the more generalized pages serve better performing ads. Doesn't make sense to me, and I am sure that the more specific sites will eventually out-perform.

Here's the explanation and it ties in to the OP's question.

Ads are chosen/targeted/displayed using a bunch of variables, but one set involves on page factors for that particular page, and another is site theme which is domain relevant.

If you have a site called widget.com which displays widgets and does so profitably (your entire site is optimized for a small number of words about widgets), you'll get a tendency to have teh same ads displayed on all pages due to theme.

If you have a more general site that is not optimized well for any set of specific words, then on page factors then becomes primary. You'll get better variation.

This is based on a response from google around why a well optimized site shows the same ads on virtually all pages despite the fact there are better "ads" that would fit individual pages.

Branding is something else to consider. The greater your visibility and branding, the more inbound links, press coverage, etc. you'll get. If you're in this for the long haul, and if you want to diversify into revenue streams besides AdSense, building a brand and reputation is likely to pay off in the long run.

Also, the decision isn't necessarily between the extremes of "a whole lotta sites" and "one big site." There can be a middle ground. For example, let's say you're a baker named Bev and you start a site about baked goods called Bevbakes.com. Under the Bevbakes.com umbrella, you could have major subsidiary sites with "vanity domains" such as Bevbakescakes.com and Bevbakespies.com, with the vanity domains pointing to subdomains (cakes.bevbakes.com) or directories (bevbakes.com/pies/).

The advantage of this approach is that it lets you establish brands (and inbound linkbait) for your major subtopics without sacrificing the ability to have a general "umbrella theme" site for topics such as breads, muffins, pastries, etc. where you don't expect to have enough content to justify secondary sites.

For any newbies, and established, this is already a bookmarkable post!

Some great advice and opinions here...just to prove we all don't just "play games" all day:-)))

Going back to the OP, I'd warn that topics like "weight loss, diabetes, hypertension" are shooting too high -by a mile or two- for a startup. Each topic on its own could be developed into a family of a few sites that over a year or 18 months could become a full-time job with very satisfactory earnings. But that's saying to pick only one of those topics, not all three.

Personally, I'd go even smaller: a sub-niche of weight loss or diabetes. You have a better chance to get first page G ranking quickly by picking tighter targets. And theres nothing that builds traffic like Google, at least in my experience.

Just food for thought, but Page Rank should also be considered. If you have 100 web sites with page rank 1 and 1 site with PR 7, it doesn't take a rocket scientist to figure where the bulk of the traffic and income is going to come from.

I'm considering a joint project with a friend, and I'm thinking of launching it on my main site, then, if and when it gets legs, going to its own domain. Probably going to grab the domain name and park it for 6 months with links back to the active pages. Does that make sense?

Fearlessrick - I have to disagree here. I have sites with good page rank, and sites with virtually no PR. I have to say my biggest earner has very low PR, however I spend heavily on PPC for this site. The site is in a highly competitive area, so to achieve a good PR and any sort of appearance on organic listings, with my limited skills, is nearly impossible. However it does produce excellent results. Once again, can't stress how different people have different results - so really good to get the overall picture on what does and doesn't work for lots of people, experiment yourself, then draw your own conclusions. :)

My website is male health, and is in the top 3 of Google for the main keyword search.

I see quite a few ads for sites that have a variety of health topics (and no content) appearing on my site, and I get quite a few requests from such sites to exchange links. I zap the health sites MFA's and won't link. I have to be honest here, and on first reading of the thread, the thought that crossed my mind was that you wanted to make a site containing a few pages on different topics - just like the sites I block! However, I do see that is probably not what you intend.

My personal feeling (based purely on the MFA's I block) is that separate domains - one per topic would certainly look more professional. If it helps maximise income I can't say! I guess experimentation is the thing.

I also have to say that the competition is tough, as you are entering the game quite late. How are you planning to drive content to the site?