Updated the main house and then built a 2bd/1ba ADU in the basement.

We can offer both in house private money for bridge loans/fix n flips as well as all your other investor loans including DSCR, Conventional, Non-QM, and Commercial. 

Sell the house as is or use the lot to build new construction and sell for 2.5+.

I mean I'm just a single guy with a 3bd 2bth SFH looking to save money by sharing the house with roommates. 

You want every single nook and cranny of the basement, as much of the roof line as can be seen, the entire property lines and grounds, the road in front and neighboring 8 houses.

You might benefit from house hacking vs. doing full STR while you are away.

I do not want the hardwired combo (more expensive and complicated to install) - From what I've read, hardwiring is required for multi-family housing, but I don't see that it is for single family residential.

I currently have ~20k saved and will have more upon the time I buy.The houses in my area are around 300-350k range. 

Secondly, because of CA laws, we are afraid the friend is just going to move in and not leave and we have no recourse. 

I know the cost is on the low side for houses.