There are a lot of considerations like setbacks, lot coverage, parking requirements, height restrictions, floor area ratios, stormwater, utilities, access etc.Assuming you can develop multiple units you could proceed with the development, set aside one unit for your father in law and sell and or rent the remaining units. 

Our units are located in the Lincoln Heights area of Los Angeles. 

If you prefer videos there are probably lots out there as well.Networking - Easier said than done with Covid 19 restrictions, but there are a lot of high quality discussions on this forum. 

Your next argument implies that during the height of COVID an average investor is collecting around 70% of rents.

My parents are in Maine and the covid restriction are stupid.

That means on a 300K property, you're looking at $75,000 down plus closing costs.If you go with a Fannie Mae Home Ready loan, that may work, but there are income restrictions. 

Most areas require a minimum 7'0" ceiling height to be considered a habitable room. 

They are quoting deed restrictions as reference now.

Any restrictions on cars per household or allowed to be parked on street overnight? 

Ya, him extending the restriction on evictions is nuts.