Hi Vligrl,
I don't recall, so forgive me in advance. Has he been dxd with any depression or anything? Has he been offered and rejected drug counseling?
In any case, he is an adult, and your home is yours. In a positive way, I guess I'd first get on the same page with husband. Then sit down with difficult child, tell him you and hubby have given this a lot of thought, and you both agree that it's time he lives like an independent, self sufficient adult. Tell him you have every confidence that he is capable of doing this, and that you both believe it would be the very best thing for him and his self esteem to be a fully functioning grown man. Tell him you love him, you want only the best for him, and you've done everything you could to give him a healthy foundation to build his adult life on, and he must do the rest from here. He's going to interpret this as you're throwing him out, so be prepared for a very scared, angry and hurt response. His feelings will be hurt, and he will bargain, plead, and manipulate you. You may also want to offer him up to 6 months to save up for an apartment and living expenses, so you can make it clear that you don't expect him to pack up overnight (you wish!), but that you're offering a realistic and workable option. Encourage him that you both think that this is the push he needs to prove that he's ready and able to pull himself up and be a responsible adult. I might offer the first and last month's rent and the security deposit to get him started off, and any furniture you could spare to feather the nest. Since he needs to work, he will oppose this and say he needs a car, and if you don't give him one, how can he hold a job and pay rent? I don't know what you would offer as a response, because I don't know how much, if anything he has saved up so far, and if you and husband would be willing to fund a car for him. I would strongly suggest you make him pay for insurance, in case he drives impaired.
Again, Vligrl, I don't know if there's a history of dual diagnosis that is impeding his transition to adulthood. In any case, he is 19 and he has to learn to be his own advocate. You and husband can't work harder than he is willing to in order to function normally. If you offer him the 6 months to save up money, you can possibly offer treatment/counseling for that period as well, and he has to agree to faithfully attend, so that when the 6 months are up, he will be on the road to financial and mental well being. Easier said than done, right?
Take your time, and just hold your ground.