First time buyer - question about the right mortgage for us

[Cameron Mertens]

Hello! I am currently renting an apartment with a roommate in Los Angeles but we have been bought out of our place and are now looking to potentially do some form of house hacking with our buyout $. The full scenario is this:

I have a girlfriend and we have talked about moving in together for a little while now. She owns a single family 2 bedroom home in Long Beach in which I will be moving into while we find the right property since we have to be out of this apartment at the end of January. Her mom lives with her and we have agreed we need our own space but want her to stick close to us. She has said she would prefer to keep this house and rent it out to keep the equity, but would potentially be willing to sell it if it will help us find the right place for all of us to live.

My roommate will be moving home while we find the right place but he's fully on board with this idea.

Because of all of these things, we won't be able to fully house hack to have our place fully paid for. We are going to search for a 4-plex somewhere between Los Angeles and Long Beach in which my girlfriend and myself will live in 1 unit, her mom in the 2nd, my roommate in the 3rd and we will rent out the 4th unit at market price to help offset our costs. If we can make the numbers work with a triplex and just all of us occupying the entire building we would consider that as well. As long as we are starting the process of paying ourselves instead of paying someone else's mortgage.

I have started trying to learn everything I can about this and because all of us have decent paying jobs but not a ton of savings, FHA or 203k seems to be the way to go from a financial standpoint so we don't have to put a ton of $ down. However, we are worried about how this works when 3 of us will all be applying together for the loan as none of us will qualify for a $800,000-900,000 loan alone. I have read a little about tenancy in common as well, but I am not sure how that works with FHA/203k. We won't be able to get 20% down for a conventional loan but I have also read it is possible for us to potentially put only 5% down on certain conventional loans as well. I am hoping someone might be able to help me with some information or direct me toward where I can find some information as to which option might be best for 3 people looking to take out a singular mortgage for a multi unit building that 3 of 4 will be owner occupied and the 4th rented out or 3 of 3 units owner occupied. If this isn't the right forum and someone can direct me to the right place that would be awesome too! Thank you very much and happy holidays!