Hi biscuitsmom,
I'm new to the forums. I thought I would weigh in on this topic from my perspective, and I hope it might be of some help. I would suggest going half way on this plan. I would extend the housing offer to Michelle, whose character you have been able to judge for 15 years, and not extend the offer to Kurt, to whom you feel no special obligation. Let Kurt stay with friends of his, or in the worst case a shelter. As a man he would likely be safer there. Allow him some visiting hours, primarily to use the computer to look for work, and leave it at that.
This way, as I see it, there are two possible outcomes. Either Michelle will realize, when she has some breathing room, that she is in a bad relationship with a nogoodnik, or their separation will motivate them to work hard to create the circumstances to be together again. Either way, I think it is a more workable situation for you and and your spouse, especially on account of Kurt tending to work second shift.
Also, make sure, before she moves in, that they each have prepaid cell phones and a p.o.box. There is no way they can get work if an employer can't reach them. Again, paying for a p.o. box and the two lines will be motivation for them to get themselves a permanent address. So, for Kurt, if he really has no cash, pay him an hourly wage for that yard work, so there is no misunderstandings about the value of that work later. For Michelle, perhaps you can loan her money to do these things, but only if you really expect to be repaid.
On another topic entirely, I don't know if you have seen the research connecting kidney disease and soda pop consumption, but you should definitely know about it. "Women who drink two or more cans of soda pop per day are nearly twice as likely to show early signs of kidney disease, a recent study has found." <http://www.elements4health.com.....ml> Please, be kind to yourself and wean yourself off the soda. You seem like such a nice person, so I wish you the best possible health and much happiness.