Could I go out and really pound the agent business and be a high income earner?

I’m no person able to give legal advise but based on what you said I’d tell the guy to pound salt !

Here in CA, the challenges to development from a regulatory perspective make development undesirable for business people who take risks in exchange for profit. 

I will hate for you to place your private funds into undesirable areas, confusing condos, rusty mobile homes or go with an unscrupulous "partner".   

The 800 pound gorillas (in no certain order)  in this space are  Property Ware,   Appfolio,  Buildium  There are other options depending on the number of properties you are managing and what you expect your growth trajectory to be.  

If you want to wait and see what happens down the road you can always tell him to go pound sand.

So, at least in my market, sellers that offer seller financing only do so because the property has major issues keeping it from being financed in the first place, or they are can't get any other offers for whatever reason (undesirable area, etc).There's a lot of talk on BP claiming seller financing is a great way to get into investing. 

However, coming at them in a disrespectful manner that makes them feel pressured, or taken advantage of will rub them the wrong way, and they will most likely tell you to pound sand, and then bad mouth you to anyone who will listen. 

The next time someone goes to rehab one of these, the only way out is to pound the contractor into the sand.

In that case, it may take longer to rent your unit or you will have to accept undesirable tenants because all the good ones can go get a nicer property next door.Pretend you are a tenant seeking a place to live and compare your property to the others.