I have a new venture im starting, social networking niche + service with a very strong following and new idea that im very passionate about and has not been done yet. Im having trouble deciding if i should charge a signup fee, it would be very low cost like 10$ per year etc.. or if i should offer free signup and try the adsense route.

Its very hard at this point because i have no traffic numbers to go by. The site will offer a very valuable service to all users and a small fee I think would not be a problmem but its very tempting to offer FREE and simply use adsense as revenue. The end user will mostly be ages 11-25 so FREE! would get many more signups.

I would hate to go the adsense route and blast FREE SIGNUPS and find that adsense is not bringing in the numbers i need and then have to rethink and change the business plan.

Has anyone tried or had this similiar problem? Obviously the idea is to reap the most from the site and finding out whether its free, signup, adsense or both is my main question.