Let me try an adjustment to the conversation and see if that helps you out a little:
In my experience, an ad like that ones boils down to - decent hull that needs some work, interior is questionable and may need a lot of work ... assume the motor is busted enough to possibly be a loss. For you - wanting to be on the water next season - can you put the potential 30 or more hours of labor in the boat, plus material cost to make it water worthy over the winter, plus purchase a replacement outboard for it?
In other words, is this boat worth the risk? $500 can be a reasonable figure to risk on a boat, but you've got to be realistic that it may mean you won't have a lake ready boat next spring. AND you may have to spend another $2,000 to get it out on the water. $3,500 and you can probably find something that will park in the garage and be pretty much ready to go next spring with some easy cleanin' and maintenance. See the trade off?
I rolled the dice on my boat - and kinda' even made a dumb buy on it - but it worked out VERY well for me. I was ready for the risk and it paid off. If you're wanting something that you can do a little repair to, and really just get it out on the water, this might be too much risk.
If you've not rehabbed a boat in the past, spend a little time looking around the
RESTORATION FORUM a bit and see what kinda' trouble you can run into. It'll give you an idea of what you might be up against.