pinayreefer, Sounds like you have a handle on it. Is the boat on the hard if so you could determine if she leaks after your sea-trial her if the water in the bilge is higher.
All boats that have been in water or the weather have water in their bilges. Hence most all boats come with bilge pumps.
In older sailboats a lot of the water in the bilge comes from leaking ports
(rain water) which you mentioned the boat has/has seen.
If the bilge pump(s) doesn't come on every hour you should be OK. Also depending on the bilge form sometimes you can't pump them dry.
Make sure you stipulate the contingencies with a subject to your acceptance and possible price deduction.
Good luck, hopefully you'll be sailing soon.