Also, while I'm making a thread...would it break the game to turn a house lot into an apt lot even if there's only the one house (apt) on the lot? I have an idea about making rental houses for low income sims, kinda like how uni houses work. Or is there a way to make a uni house lot outside of a uni hood?
No, you can turn a single family dwelling into an apartment without breaking anything. Most of my tiny apartments (link in my sig) are just that.