You're kidding right?
You'll be into an LT front end for a Banshee for at least $2,000, if not more, depending on the brand of everything.
A good rear shock is $800-1,000. A MX swingarm I guess to be in the $500 range.
Chassis work, regardless of what you're getting done is going to be at least $1,000, if you truly want anything "modified."
A bolt on sub-frame is $2-300.
Then there's the odds and ends shit that add up quick.
I'm not saying I blame you for not wanting to spend money, but I think your price range of a fully setup MX style chassis is fairly skewed.