I dont know about that...
The biggest thing is that you have to keep an eye on the carbs. As soon as you et it take them apart and make sure its jetted right. The only weakness with Banshees, and 2 strokes, as far as maintenance go is that it is easy to fuck up if the jetting is wrong. Having the right jetting, and making sure the carbs are right will solve 90% of your headaches.
Other than that, a Banshee was my first big quad. I had a Kawie Mojave, and a couple dirt bikes before my shees, and I dont regret it at all. The only time the bike was ever tough to work on was when I was just learning it, and I got a shitty bike to boot. If youve ridden 2 strokes before it shouldnt be an issue. If your not a complete noob, or an idiot it shouldnt be an issue.
1800 sounds like a good deal for that bike, just look over all the usuals, make sure the bearings/seals/engine is good. Maybe even do a compression test if the owner will let you. Good luck bro....