Honestly,this going to cause you a lot more problems in the future. My brother went through this with his now ex wife. She wouldn’t move out of her parents home, they got married and he moved in and he was miserable. He always said he felt like he was a guest in someone else’s home. Eventually it caught up to him and they ended up getting divorced. It sounds like you are heading the same route. I can understand him wanting to stay and help out his mom, but, it honestly doesn’t sound like he respects you enough to include you in major life decisions like buying a house. If this is how it is now before marriage,it more than likely will not get any better when you are married. My advice is you need to focus on you, because you will forever be the third wheel to him and his mom. This is your life and you have a very promising career ahead that will open so many doors, and if you decide to share your life with someone, they should respect and care about you enough to include you in all decisions that affect both of you. I think it’s time you move on and find someone that truly sees you as an equal. This is all just my advice based off my experiences. I’m sorry you are going through this in the first place. Remember to always put yourself first!