The $15,000 boat looks like a deal. By the time you add the bottom paint, the running rigging replacement, the engine service, the two through-hulls that are leaking, the standing rigging inspection and certification, the new sails, the safety gear update, the electrical work, the slip deposit, and the first year of insurance — you are often at $40,000 to $60,000 or more. And that is before anything actually breaks underway.
Cheap boats are almost always cheap for a reason. The previous owner ran out of energy, money, or both. The deferred maintenance got deferred long enough that it became someone else's problem — yours.
This does not mean avoid cheap boats. It means price the whole boat, not just the purchase. Before you fall in love with the purchase price, build an honest ownership cost model. What does it need right now? What does it need in the next two years? That number — the real number — is what you are actually buying.