Can Private Room Upgrade to Private Housing?

[KaiKatzchen]

Hello, I hope this can be answered at some point~! We were talking in our FC and some were saying they wanted a Private House and were sad they had to wait for them to come out. The conversation turned to two things, which are the main questions that we were wondering:

1. Can you get a Personal Room and then pay another fee to upgrade to a Personal House later?
2. Can you own both? (buy a personal room now, and still get a Personal House later?
   
   or is it
   
3. You have to pick, Private Room now or wait for Private House later.

Thank you for your time and any answers you might be able to give. <3