Go to court and get an eviction order, saying you have 30 days to either start paying an agreed upon rent, or they can get out. Job Corps should have already sent notice when he is due to go. Normally, within a month of signing up (at least when I went) I was on my way. I'd check to see if he even signed up for JC.
Depending on where you live, see that after the 30 day period has expired, can you get him (and his little girlfriend, too) for trespassing. If you want to really be nasty, since she is living there, see if you cannot garnish her wages.
I think that after those two kids get a dose of reality, they'll either straighten up and fly right, or they will fall on their faces. Either way, they will end up in need. Then you should sit them both down, draw up a fair lease, and they can either sign it, or they can look for another place where the landlord will not only boot their behinds out, but sue for remaining time due, money for damages, and keep their deposit.
It may sound harsh, but I think they both are counting on your kind heart not to boot them out, take them to court, etc.
They are not learning any responsibility right now, and if they do not learn it now, they will suffer for it later. Good luck.