I would want to see docs regarding HOA. Since it’s 4 units total – 2 commercial, 2 residential – how the maintenance is handled is important.
I would want to know the status of the other 3 units. Are they already sold? Are you the first buyer? Financing might be challenging if you’re the first one. Not sure if that owner occupied rates apply to 2-4 unit developments.
Has the builder obtained occupancy permits yet? The big clue there is whether the gas meters are installed. (At least in the city of San Diego – sdg&e is not allowed to install the gas meters till occupancy permit is issued.)