Re: is it worth it?
I'll answer the question you didn't quite ask I think:
It's worth it to restore a boat if you A) have emotional attachment to a particular boat or B) You like doing the work as much as using the boat.
It's NOT worth it if you're trying to save money, or trying to get on the water fast.
The best way to start out picking a boat is not to get too fixated on any particular one you're looking at.
Look around, in this economy for $500 you should be able to find a boat that is functional, with engine, trailer, and hull, all the glass intact, interior not totally wrecked, etc.
At that price, though, you're going to get an older boat, or one that was catastrophically damaged. Expect and plan to remove and replace stringers, deck, and possibly the transom.
Don't take the seller's word for it that "it's good". Most sellers don't know jack about the condition of the boat, and have a heavy emotional investment and financial interest in believing it's in great shape and worth more than it is. Even if there's signs of rot, they won't look for it and won't see it if it's in front of their face... and they won't thank you for pointing it out.
Even when buying from a friend or relative, assume the condition of the boat is unknown even if you know they've taken decent care of it until you have it professionally inspected or, for cheaper boats, inspect it yourself. They may not deceive you intentionally, but they might deceive themselves.
Negotiate, don't be afraid to walk away and think about it, especially in this economy. It's a buyer's market and then some.
Make sure as part of the sale you get a title to the boat, and possibly a title to the trailer and engine (if your state titles outboards). Without this, don't put any money at all in the boat.
There are exceptions to all of this, of course.. but your odds of finding one are only slightly better than winning the $10k lottery. Everyone wants to believe they've found the one non-rotten classic boat at a bargain price that won't require a ton of work to use but which will be worth many $$ if shined up and cleaned. You won't, sorry.
After your restore you will have a boat that's exactly the way you want it, it'll be fun to use and look great, and you'll have a lot of pride in having done the work yourself.
It won't be a good investment... you'll never get your money back by selling it unless you're either very, very lucky or you manage to get one of the boats in high demand by collectors (like the old mahogany runabouts, eg.).
Erik