Bedroom help

DR

My fiancé and I are currently looking to buy our first home YAYAA. We’re knee deep in all this crap it’s overwhelming af.

However one thing I’m totally going back and forth on.... we are raising my two girls who will live with us full time, and would like two more children together. We are trying to get visits and weekends (the weekend part once we buy and settle into the home) with his four year old son. How many rooms should we be trying to have I think 5, he’s open to 3 or 4.

I feel that the girls shouldn’t have to share a room because they live with us full time. I don’t feel that it would be fair that his son wouldn’t have his own room (also would be a guest room when he is not with us) so I feel that we should really not look under five bedrooms. However I feel that it’s like a tit for tat. We go for a bigger house we get less of a yard, we might have to go into a neighborhood that the schools are not the best. If we go with a four bedroom we could have a bigger yard and be in the best school. But what happens when we have a baby where would the baby go we can’t give a kid his own room then take it away?! I’m trying to be considerate to his son and all of the kids. This is like the biggest purchase we’ll ever make (we want to live in the house until the last kid turns 18 and goes onto college). So can I get some input and advice?!