Allow Dude to stay at our house after maxing it out.

[Vagabond]

Honestly, this is the best motivation to buy everything there is, so that Dude can finally have a proper home, and to put a cherry on top. Add a small buff after achieving it, like an additional 5% to crafting or maybe a new item crafting/buying added, or allow dude to auto-leave a cold Juice in the fridge in exchange for Brew every so often.

I wouldn't mind other characters to join in, but for now Dude is the best candidate.

[Orthrus03]

I think that Coral should move in after you max the place out. It would be in keeping with her character, definitely.