Same here, bought a 22 foot trailer sailer for $400. Spent a couple weeks cleaning it up, painting,and doing a few small repairs, then spent the summer out sailing on lake michigan. That fall I sold the boat and trailer for $2400 and bought another cheap boat and did the same the next summer.
Trick is you have to know what you're looking at, don't want to pick up a cheap boat that ends up having serious issues. I've seen perfectly sound boats sit unsold at low prices because of cosmetic issues, while boats that looked great, but had more serious problems sold for a lot more.
Also depends a great deal on what you want out of the boat in the first place.