I can't imagine there are many sucessful start-ups that didn't go through at least a couple of iterations before landing on the ultimate model.
Oh, but if you don't have cash, then its hard to do much.
You don't need lots of cash to do a web startup - for many anyways. What's hard to find is the time unless you want to drop everything and focus on that. My other main problem is finding people. It is a herculean task to find someone willing to work on a startup and I don't even mean for equity. I can't even find talented people who I would pay who would do work on some tasks for my startup. Most people, really talented people, are content w/ their day job and dont have time to humor startups.
I had some luck finding people overseas. The people I found in the US were often those who I wouldn't want working for me.
This is a quintessential example of why I would like to see subdomains included in the parenthetical note beside the title. Not that the link was bad, but I initially expected it to come from the posterous founders' blog.