Stiff steering can sometimes be remedied by greasing the system or repairing broken pulleys, but if the steering system needs replacing, it can be expensive. Check for required safety equipment. Make sure running lights work, the fire extinguishers are charged, flares are not out of date and that it has an anchor and anchor line. Inspect the propellers. If they are damaged, plan on replacing or repairing them.
Repairs are less.
Remove covers from cockpit and cabin cushions and see that the foam inside is in good shape. In smaller boats with cockpit seats that lay flat, look underneath to make sure the plywood isn't rotten. Damaged seats can be recovered or replaced, but they might be a negotiating point. Examine cleats and other deck fittings carefully. They should be bolted through the deck, not screwed into the fiberglass, and backed with wood blocks or metal plates under the deck.