Right so me and my friend were playing last night and we decided to go see if it was possible to get into Michael's house. At first we had nothing since the doors are all locked but then I remembered that you can glitch open your garage door by leaving a car by it, moving away until it unloads and them coming back so that it loads open due to the car being in the way.
I did this and it actually worked. I got inside Michael's house and was able to explore. We then tried with Franklin's second house but his garage isn't connected so it didn't work.
Has anyone found any other way of getting into interiors?