Build your audience first...not the product.

Check out Amplification (http://buildandlaunch.net/book/amplification/) by Justin Jackson (http://twitter.com/mijustin)

I own FindSpotter.com (a hugely profitable membership site for Amazon merchants). My suggestion is: join a membership site in the same/closest niche, kick the tires, then (most important) talk to other members what they like/dislike, and build a better mousetrap. Plan on investing a little $ (don't expect to get everything for ultra-low cost/free) to make a true 'business' out o fit.