Sure, you can sue them (or him) in small claims court.
You'll probably prevail, but then you have to collect on your judgment.
He's homeless. He's a deadbeat. He's a moocher. He's a leech.
You'll never see a dime of that $500.
Plus, you'll lay out another $100 to pay for fees and costs required to sue the bum.
Be smart, just don't ever get snookered by some bum's hard luck lies.
Let it go, and don't throw good money away chasing bad.