Depends if you’re going medical or recreational.
Recreational has to be provided by a licensed recreational grower. You probably will not be able to take this route in LA, but can find jurisdictions in So Cal that do allow it. You can find most of the info on the CA Dept. of Food and Ag. You will need a place to grow that meets the requirements set forth by the state, and you will need to find a jurisdiction that grants permits in the classification you are looking for. Then you need a site layout, business plan, etc., etc...
It is no easy feat. I have a buddy going through the wringer to become a processor. He has spent almost $18k between consultations, realtors, lease applications, permit applications, and all that jazz. Still a long way to go, but there is light at the end of the tunnel, and shows that it can be done by your average Joe, so long as Joe has the pockets to keep up with California legislators. You need deep pockets and patience.
Medical can be provided by just about anyone with a license. This is the easier route, but there are fewer dollar signs involved.