Advice needed- step mum problem’s

Me and my partner are expecting our first baby together, however my partner has a 5 year old from a previous relationship. We all get in great no issues with that. The 5 yr old is great and we get on really well. She doesn’t live with us and due to work commitments and her being at school etc we only get to have her every other Sunday.

Due to financial issues my oh and me have had to move back to my mums house. A 3 bed house. We have a spare room which we are turning into a nursery.

However my partners daughter has quite a lot of toys etc that she keeps at ours And we are rapidly running out of space.

We have a shed and I suggested putting some of the daughters stuff in a box and putting them in the shed. My OH wants to put some of it in the nursery, but the selfish part of me wants our baby to have his own room. His daughter didn’t have to share her bedroom when she was born and I don’t see why our baby should have to either. Plus as she isn’t there all time it’s taking up space that will be needed for baby things etc. I’ve said some things can go in but not everything.

It’s caused a major argument. My oh thinks I’m being selfish, which to a certain extent I am. But this is my first baby and I want him to have his own room and a room I can go in with him to feed etc where we won’t be disturbed etc . I don’t know what to do! Help please