It's a crappy *mart department store bike. either a magna/next/etc variant.
These things cost 80$ new, and are not worth repairing.
-I work at an LBS, we charge 20$ for a flat tire fix; when I see one of these come in with 2 flats and the rear tire with no tread left, I tell them they might as well just trash it and buy another one.
get the hint?
Don't buy it. I wasnt a good bike new, and certainly isnt any better all beat up like that.
I wouldnt even take it for free, it will only be a sinkhole in your wallet to try and get it to work.
Check craigslist. whats your region and how tall are you? I'm feeling magnanimous so I might as well browse the listings and point out a few decent ones....