Op your ds sounds scarily similar to my ex.
He had his good moments but the way he treated his mum and sister was absolutely disgusting. He had absolutely no respect for either of them, everything had to be his way all the time. If he demanded something everyone else would literally drop everything to help him out. As an example, we were eating dinner at his mums one night and he couldn't find his lighter. He started shouting and swearing and saying that everyone HAD to help him find it RIGHT NOW. So his mum and sister both stopped in the middle of eating dinner and starting pulling the sofa cushions off, looking around on the floor etc for the missing lighter. I was absolutely stunned watching it. It was eventually found and instead of thanking them and apologising for making them stop eating, he instead blamed them for the house being such a mess he couldn't find anything.
He never once lifted a finger in the house, never cleaned anything, made a meal, or tidied up after himself, his mum did absolutely everything for him. If he ran out of tobacco or weed, he would demand that his mum or sister drove him to get some more and give him the money for it (since he wasn't working and had no money of his own). She did it. When he stupidly lost his car because he was driving without insurance, he demanded that his mum pay for a now massively inflated price wise whole year of insurance payments upfront so he wouldn't miss another monthly payment. She did it. When he had to move back home to his mums house, he insisted that he take the largest room (her room) because the other rooms weren't big enough to store his mountain of useless junk. Did she make him get rid of stuff or give him a smaller room? No of course not. She gave in and ended up giving him her own bed and sleeping on the sofa because the single bed she bought for him was too small and he didn't like it. She got him on to a college course and paid upfront for the whole thing. He didn't bother going. He was an absolute pro at guilt tripping and manipulation, and would make his mum feel terrible if she dared to say no to anything he wanted so she always ended up giving in.
You might think that this person was in their late teens, maybe early 20's. Sadly not. He was 30. He has recently fathered a child and I'll bet you a million pounds that mummy ends up doing a lot of the child related stuff that he can't be arsed to do.
In both his and your cases Op it seems that the problem really is that there is no consequences for their behaviour. They can keep treating people like crap because they allow it. No one says no to them. Please, please do not let him live in your new house. He won't change unless he is forced to, he needs a heavy dose of tough love to sort himself out. It was absolutely heartbreaking watching my exMIL run herself absolutely ragged trying to please him, when despite all her efforts he was just as rude, aggressive and lazy as ever. She deserved so much better, but she also had the power to force him to grow up and change she just couldn't muster the strength to do it.
Good luck with everything, it's a really tough situation to be in and I really hope it works out for you x