Off topic- roommate

Sorry for the off topic post, couldn't find an advice group. Back in September, my husband's old friend showed up at our door while he was at work. My husband had been friends with this guy for 15+ years until he first doing drugs (meth) and no one had seen him for maybe 2 years. He had just been in jail for 6 months, and didn't want to go back to his girlfriend that started him on the drugs. He had no where to go. My husband said he could rent the extra room in the basement, but he had to be 100% clean and if not, he was out the second we found out otherwise. He got a pretty good paying job just a few weeks later (around $600 a week, sometimes more.) Well, 2 weeks ago he got pulled over for speeding and had a warrant for unpaid fines. Since he's on probation, they gave him a drug test and he failed- for meth. He kept calling my husband looking for a ride when he got out, and my husband texted him something along the lines of, we had a deal and if drugs are more important than a place to live, let him know and we'll arrange someone to bring him his stuff. He said was never doing drugs again, that his p.o said if he messed up again, he'd be doing his 3 year prison sentence. He said he save $200 out of his last check (gets paid weekely)and he'd have the rest today when rent was due. He's been gone the last few nights, and showed up today with $50 of his $300 rent money and said that's all he had. My thoughts are, I want him out and don't care if he doesn't have a place to go. He failed his drug test, plus can't pay his rent. My husband doesn't think he can tell him to leave unless we get him a drug test and he fails. I'm done babysitting an almost 30 year old that doesn't care about his self, and can't understand that I will not allow drugs in my home, and my sons home.