How would I change parts of a level?

Hello. I’m just looking for a general way to get started, my game is a top down pixel art RPG made with paper 2d.

I would like the player to be able to purchase upgrades for his house inside of a level.
Another example would have the player buying a couch from a shop and then having it appear inside his house when he gets back home.
Or maybe have the player pay to have the town bridge repaired at the shop and then being able to cross to the other side.
How would I go about this process?

Thanks in advance,
Adam