I would have to agree with Brian on this answer, that determining the features you need to meet your markets needs is the first place to start. Providing you with a black and white answer is very difficult without having more specific specs. I would be happy to sit down and review everything with you and help you determine the needed features, the nice to haves, and estimated costs associated with each. There are a number of different directions you can go in even the initial development and hosting etc, which would effect even your ongoing costs. Send me a message if you would like to discuss further, as I am quite certain I can assist you in determining your early stage needs and send you in a direction that will help you out. WITHOUT costing you an arm and a leg just to get your feet wet and test out your concept.

Take care.
-Branden
nadimo.com