This borders on the free boat no one can afford.
You'll need to make of a list of deal breakers. Those things too expensive to replace or fix. You'll soon spend a lot of cash and you may want to look at lower priced boats that are worth more than $500.
A full interior
means all new plumbing
work, fridge, lights. Then the deck hardware
(and the attachments to it), sails
. I would assume if you save a winch
or two you'll be doing well. Just do a quick math on the total cost of these materials and you'll soon see some free boats are not worth it.
As noted above one or two serious structural problems and it might no longer be a boat. If you even think you need advice
on if you should buy it then the answer would clearly be no. The little things you never think of will be at least another $5,000. if you plan to cruise
you need lots of stuff that isn't attached to the boat too. Anchors and rodes add up fast.
I really think $20,000 would put you into the game
on a boat that would cost less and be done far sooner. If you have not got that much in hand you'll never see the end of the tunnel on this one. I'd also look at a CD 30. Even if you don't need much you'll need to carry a lot of stuff.