Actually the right answer is, you can build another house but in the same and the only lot/land you have right now. If you watch a youtuber video, she build 3 house (separately), a very nice design I will say.
Du KAN.Jeg er kun i level 11, og jeg har to huse. Et med en etage og et andet med to.
I really don't know if this was a fever dream or not but I think I saw somewhere that you can now add second floors to your house in sims mobile. If this is true will someone please tell me because I can't see the option in build mode and I don't know if I'm going mad!
Go to the quest and click on the little question mark in the top right corner. It will tell you what you need to do. Usually you have to click on a specific piece of furniture in your home such as a table for example, for the option to appear.
Can I sell my house and buy a different one, it says I unlocked a new house.