If things are not working out now, what makes you think that they will get better if he moves in with you? If anything, they'll probably get worse as you have already experienced this in the past. Having him move in with you will make it a lot more difficult to get away from him if you need to.
The fact that he doesn't have any money is a huge red flag. What is he spending his money on? If he was serious about moving in with you, why hasn't he saved any money to help with the expenses?
Addicts are very good at manipulating people. There is a term called FOG which stands for Fear, Obligation and Guilt. Sometimes our minds are so wrapped up in this FOG that we can't see things clearly. All of our time, thoughts and energy are focused on the addict and we end up neglecting ourselves. Why do you feel responsible and guilty for HIS problems? He is where he is because of his CHOICES and he may be trying to guilt you into thinking this is somehow your fault.
No one can tell you what to do, that's up to you. But if I were you, I wouldn't even consider moving in with him until he SHOWS me that he can get his act together and keep it together for a long period of time. Words are not enough, he has to follow through with his actions.
I recommend that you read the stickies on this forum. They may help you see things more clearly. I hope things work out for you and that you'll keep coming back. I have received a lot of help and support from many people here who know what it's like to live with and love an addict.
Hugs