What, if anything, should I do?

My BF (who is over 40) got a new neighbor (Mike) recently who is unemployed but swears he has "multi-million dollar deals" in the works.

My BF has loaned this loser about $30,000, including paying his rent 3 times. All on the promise that he'll hit it big.. soon.

(I met this guy one time and I thought he was a complete liar and a fake)

I don't understand why my BF feels so responsible or sorry for the guy. He's a shyster who also took money (a few thousand) from another neighbor. Now the woman is demanding her money back and my BF stepped in and said he'd pay her back if Mike can't!!!

Mike has promised he'll be getting 'big money' by the end of he month, but he's said that before. It won't happen. June will come and not only will Mike be wanting more money, but the other neighbor will expect my BF to repay her too.

My BF's family thinks he's crazy and so do I.

When he told me he paid Mike's rent again for May, I zipped my lip and my BF thanked me for not voicing my opinion.

I can't stand to see this happen.

What can I do or say, if anything????