Yes, it's possible to get a great deal on a blistered boat. But there are also many cases where the buyer has regretted buying
The decision to buy one has to be made with the best information available, using a very reliable surveyor:
If the blisters are structural, walk away.
If the blisters are cosmetic, what is the worst case cost:
1) of repairing the blisters (frequently this will involve a peel)
2) of drying out the hull, including storage
(this is potentially the largest component of the total cost)
3) of sealing the bottom and then applying bottom paint
Do you still want the boat after adding this up and taking into account how long you will be unable to use the boat while this goes on (certainly several months, maybe as much as a year) and thinking about how many other attractive boats might become available during that time?
If you still want the boat, increase the total cost from above by at least 25%, add it to the asking price, and start negotiating. If the seller won't negotiate with you and give you an attractive price, walk away. You'll be out the cost of the survey, but you will have learned some very good information.
Also, do not buy the boat unless you will be able to closely supervise every aspect of the total repair. One of the few advantages of buying
and repairing a blistered boat is knowing the repair job was done right.