I bought my '88 650sx in the beginning of the summer. It might be a crappy ride but since I don't know any better, I think it's a blast. It has plenty of power for a beginner and it runs solid. I'm very happy with it. I paid $800 and $160 for the trailer. It has some upgrades and etc, in FL.
Be careful though, with the old skis, watch out for the bad parts. My ski runs good, but with a bad motor mount, bed plate, power cord and exhaust header, I'm at $90 in repairs and that's with the motor mount and the exhaust still messed up. Just remember that if you try to go too cheap, you might pay for it in the long run.
I'm still very happy with it and glad to have it.