Any suggestions?

[Hypno Rider]

Hi guys, I just picked up a 1999 GZ250 with 2000 miles on the clock, here is the story: I got it from a friend for $200 bucks. He said he bought it from a motorcycle training school for $700 bucks because he needed something to practice on to get his license. The bike is not running. He said its been sitting for a year outside in the yard uncovered. He showed me a video of him riding the bike about a year ago, right after installing a $15 dollar eBay battery, and she fired right up strong and was riding perfectly, and that was after sitting for a couple of months. Also, very oddly, the bike has definitely been sitting but the tires have not deflated. They are still full of air. The seat is a little loose and shaky, the exhaust pipes are rusty from sitting in the rain, the gas tank is a little shaky and pretty dinged up and I don't have the keys. Other than that,she looks pretty good :2tup:
What do you guys think I should be focused on to get her up and running? All ideas will be greatly appreciated. Will a 2004 ignition fit a 1999 GZ250? Why would the gas tank and seat be loose? Should I replace the pipes or just try to clean the rust? Thanks in advance for any help guys.
P.S. I missed the most important question: should I start the work now? Or should I just wait until after the new york winter?