that black OBS looks and sounds to be as good an early Impreza as you're likely to find. The owner doesn't even know what he's got...no GC series OBS had the 2.5, all were 2.2s. Car has had a munch of recent maintenance, etc etc. If you are "too busy" even to call about it, wtf dood?
you should probably just go and get a newer car at a dealer. it's pretty clear that you have too much indecision and not enough experience to manage buying one thru a private sale. this thread started waaaay back in April, and you still don't have a car??!! this is not a hack on you, just an observation.
your mom is being sensible, spending a bit more $ up front to eliminate surprises, which clearly neither of you want to deal with, or even CAN deal with. On a private sale, ANY problem is your problem. With a dealer, you got some backup.
once you've had the car a while and get to know more about it, and accumulate some-real world experience (as opposed to hanging on MS kind of experience) then you'll have more confidence and the skills needed to go out and seek interesting gems in the private-sale market.