Why don't you just go buy a new one? Take the funds you have and drop them down on a new bike that comes with a warranty that nobody has screwed with. You'll have a bike that you know has no issues. One that was never ran low on oil or ridden hard and put up wet. See what kind of payment you can get on a new one. It might be less than the repair costs you'll encounter with a used bike.
“Take the risk of thinking for yourself , much more happiness , truth, beauty, and wisdom will come to you that way.” Hitchens