If the framework is different and only the specific property content is the same, I think you are OK. The property data will (hopefully) change on a regular basis.

I wonder if one site would be better. I would cater to the renter and offer the owner an link to the listing section. If I were an owner, I would pick a site to advertise on based on what the offerings look like. In my mind they need to be on the same site.

I don't understand why you want to make this two different sites. I think that will just confuse people. Everyone is used to the idea of listing sites that join buyers and sellers.

I see that your goal is SEO. "listings will be optimized with different keywords". Why would property owners be searching listed properties, though? (Unless they are researching the competition.)

It seems you are trying to solve a problem that doesn't exist.

You don't intend to keyword-stuff the listings on the "owners" site with "list your property", etc.? I think the search engines will spot that in a second and slap you down good...

The reason we want two different sites and two different domain names is that we currently have a domain name that is related to our vacation rental industry that we have not used for awhile. It has been online for 5 years and is given a reasonably good page rank and is out of the sandbox. We think with some links work it will show up well in the prime search engines.

We want to use this site, which is a .com, as well as another new country specific domain.

Our goal is to be able to attract renters sooner, by showing up on the search engines more rapidly, with a seasoned domain name that is out of the google sandbox.

The owners may also have a objection to the name of the .com, which is a curious mentality thing around not acting proud or boastful about yourself, as the url starts with "grand". The renters live around the world and this is not a issue for them but maybe for the owners of properties.

This is our reason for taking this approach.

Thanks-

It seems to me, though, that you are going to have to tell the owners that their listings are shown on the "grand" site. To not tell them would be dishonest.

If you want to increase their comfort level by not having to look at that URL, you could still set up the new domain, and put the marketing pitch for sellers, sellers FAQs, login for sellers, etc. on the new domain.

Just don't make the listings browsable by the public on the second domain, in order to avoid the duplicate content policy.

But I think that more of what you had in mind was to transition to the new name, but try to garner some traffic from the old, objectionable domain name.

In that case, you should 301 redirect from the old domain to the new. Either maintain the same URL structure, or also reorganize the URLs at the same time, by using multiple redirects.

This will transfer the PR from the old site to the new one.