Just call a local real estate attorney , they will draft up a note and deed of trust for you for a fee :)

Additional Fees. 

Some of these bookings we get through marketing partners who build these relationships and charge referrals fees for finding the housing.

But it should only be attorney cost, the deed and recording fees (few hundred) , maybe a final water cert.

A lot of folks that work this are simply brokers and will make a fee for putting you together with Kiavi or lima one..

Myself I think if one wants to get into real estate in CA you get into the bizz you get licensed so you can legally collect fee's you put in the hard work like most wholesalers have to now..

You can do whatever you want in terms of bending for the tenants and trying to provide "great service,' but the truth is you receive no credit for it and will be the evil landlord at the first repair that takes too long, late fee owed, alternation denied, etc.  

I was told that one of the most important factors is the deal.

Protecting your asset is sometimes a  factor in an upgrade.

ADUs can significantly enhance your property's value by adding living space that can be used for rental income or as additional living quarters for family members.The increase in value from an ADU can vary widely depending on several factors such as the size, quality, and functionality of the ADU, as well as its integration with the main property.