There are a lot of ~30' $20,000 sailboats I'd cruise around the world in. Most of them were built in the '60s or '70s (some even newer) and are priced low because of their age. All of them would need some work done for peace of mind- usually a windvane, new sails, and occasionally a repower.
A knowledgeable friend, or a marine surveyor, will be able to determine exactly what condition the boat is in, and what sort of value it is.
Remember- the only thing more expensive than a cheap boat, is a free one