How to sort out rooms with baby

R

My partner and can only afford a three bedroom house. He has two kids, one girl aged 6 and one boy aged 8, and has them every other weekend. We will have one room and they will have one room each for when they stay.

We are thinking of having a child eventually and wondering where we could put the baby? I know for the first year or so of it’s life it can be in with us, but then what?

Thanks for your advice x

Edit:

Thank you for the comments so far!

So if the older kids share a room, should this be started immediately when we move in? Or wait until we start trying in a few years?