Interesting - I've just read the listing you quote, and whilst he goes into a fair amount of detail he's very wrong about the fork seals, and I'm sure that wfooshee will agree.
If the fork seals leak, the fork oil is depleting every time the forks compress. This won't feel bad for a while but after some time you will cease to have any damping on the forks.
Leaking fork seals are a major negative. Either he replaces them, or step away from the bike! If he says it doesn't affect the ride, he doesn't know anything about bikes.
Also, I don't know what the law is in the US, but here in the UK older vehicles need to be safety checked every year (the MOT). Aftermarket cans, unless labelled 'For Road Use' are illegal and have the potential to get you into trouble. If you buy a bike with an aftermarket can, make sure you get the original as well.
Has he replaced the engine himself? If so, based on what he says about fork seals, I wouldn't trust him to have done a good job.
That bike, in the UK, from a dealer, is worth no more than 1,000GBP.
I know you're desperate to get out there on your new wheels, but I'd look at something else. If it's anything like the UK, there are plenty of good deals to be had. If you have 2,000 dollars to spend on your first bike, my suggestion would be to take those dollars to a reputable dealer, then if anything goes wrong, you should be protected by a warranty.
I say this because I've been in your position in the past, and it's cost me a lot of money putting right other people's 'improvements'!
One final thought - a custom paint job more often than not indicates a crashed bike.
Take your time, relatively speaking, you have plenty of it left! đź‘Ť
Just been scanning your local area - no end of cruisers! This was amongst them though:
http://www.cycletrader.com/find/listing/1995-Yamaha-YZF-600R-95177383/?ZMC=Oodle&BAC-Oodle
Far safer bet than that Katana! I fancy that myself. If you offered those guys 2,000 dollars, chances are they'd take it.