Re: looking to buy a 1969 columbia 36 footer
A couple of things....
Don't do anything until the owner gets the engine running so it can be checked out.
Sanitation requirements aren't just some states, they are federal requirements and you can't discharge untreated waste, so you need either a holding tank or some kind of waste treatment system and even with that, there are "no discharge zones that don't even allow for treated waste, so a holding tank is your best bet.
Have you taken any boating courses? I'm guessing not. You need at the minimum, a boating safety class and preferably, a seamanship class.