I bought my first boat a little over a year ago. It's a 16'6 1988 runnabout with a 90hp johnson, paid only $1600 for it because the guy who sold it was in a pinch. I put a heck of a lot of work in to it, things like built a trolling motor mount for the front, added some new lounge seats, a deck in the bow w/ pedistal seat, a livewell, depth-finder, and a couple of batteries. It might not look like the baddest bass boat on the lake, but fishes in comfort and style. It may get a few strange looks at the ramp, but I tell you one thing.... I have more fun on the lake because it's paid for!
My advice: Buy in the fall.... 'cuz thats when people like to unload their old gear in anticipation of new gear in the spring. Pluss the market is tighter on the seller because only fishermen are thinking about boats or the water, everyone else is thinking aout the holidays, thus driving the price down a little. Also it's better to buy a fixer-upper than to sink into $x.xx debt for something that that you might want get rid of in a couple of years (remember all debt is bad debt). Take your downpayment and pay for the boat outright, then take the monthly payment you had planned to finance, and use that to fix up your boat. If you have to, buy a john boat and "trick her out" by adding a trolling motor, etc. The is a link here somewhere that has some good tipps on that...
Overall, take the plunge. I was a little apprehensive when I bought my boat, but it it has been the best money I have ever spent.

Keep on chuckin'