With out a picture and a way to look at the leak, it is hard to say if easy or hard fix.
I'd probably pass on this boat, as you can find better kept up boats of that size.
Other brands, Catalina 22, San Juan 21, Balboa, Aquarius, O'Day off the top of my head are all reasonably found TS's like the one you're looking at too.
She drives me boat,
I drives me dinghy!