There is a good article on this here CLICKY
On the subject of interior work. Sure buy something with NON STRUCTURAL PROBLEMS and go sailing while you fix it.
I will always remember someone who had bought a boat with bulkhead rot. He disappeared inside with a sawzall and a grinder, appearing at regular intervals to fling bits of rotten plywood into a skip. He climbed down at the end of the day satisfied with his labours only to realize with horrer that his boat's hull now had strange depressions and hollows. He never got it back to being fair.
There is a good site on working on Plastic Classics here Plastic Classic Forum ? Index page