Based on your description the bike is probably not worth anything in terms of money (actually a negative sum is most likely). Buy a new bike if you want to save money. If you want to learn about bikes, it is worth bringing it back up to speed. It is also possible to trick it out with parts or your choice. I suspect the owner just dumped it. Look for engraved police numbers on the bottom bracket ect. Perhaps leave a note where you found it.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.