Living with MIL/FIL, need support

So my SO and I have been renting for three years and the landlord doesnt want to fix anything and I'm honestly tired of throwing my money away to pay for someone elses mortgage. So we have decided to move in with his parents which is not ideal AT ALL! I think being somewhere we dont want to be will motivate us to save our money to put towards a new house. Its hard to save when we pay so much out for rent. Which is the goal for us. I do have concerns and this where I need the support. Neither of us want to go to his mom or dads but it seems the only way to save money. His parents can be greedy and we told them before hand we would help them in return but what is too much or not enough? They already have two other adult family members staying and spliting the rent with them. We are going to be using the partially finished basement with a bathroom and one huge room where my 3 kids are going to have to shack up with us for a few months.. My kids for the most part have shared parenting so they are with their dad half of the week and but my SO has kids and when they arent with him they are with his mom and dad and I honestly feel like now its going to be extremely hard to get any kind of one on one time or privacy bc now his kids will be around 24/7 while I still get a bit of a break not having mine all the time. I feel like this living situation is going to be stressful as crap and im not trying to sound crappy, I just feel like its going to be super annoying and I dont want anyone playing in or going into "our room" when were not there just bc we do have personal belongings and now were going to be confined for a little bit. My kids are in elementary school/daycare during the day and his are not so they stay with his parents during the day. (Reason why they are at his parents somedays during the week) we both honestly dont know why their mom doesnt have them or where the hell she even is. Tell me how you guys have coped and gotten through. I need it. We are expecting our own in 4 months and probably be with his mom and dad at least 6 months. To fix our credit and save money. I just know im going to get irritated bc their are times I just dont want to be bothered and I wish I could bring baby home to our own place but i know thats not going to happen but im trying to be positive and tell myself its just this one Thanksgiving and one Christmas we will be sharing with his family after this its all us and it will be worth it.