I'd say to read up on blisters, then if you are still interested hire a surveyor.
Blisters may or may not be a problem, depending on the reputation of the boat (hull and time), how many, how large, how extensive, and what was done or ignored about them in the last 4 years.
Resale? Well, apparently someone tried to buy or sell the boat 4 years ago, and now it has been up for at least another year without a buyer.
Read up, and if the price still seems right, get a survey.