@Prashanth Mahakali @John Warren thanks for the valuable input!
@Prashanth Mahakali when you say "based on zoning, only a single family can be established", are your referring to the Zoning District the lot is in (e.g RS-3, RT-4, RM-5 etc)? Or are you referring to the # of units on the Certificate of Zoning?
As @Ryan Monty mentioned above, I've seen legal 3-units with un-zoned/un-permitted basement unit (Cert of Zoning, building permit records, and assessor's data say 3-units) in RS-3 districts (which don't allow 3-units). In this case, would the buyer be purchasing 3 legal units and 1 "may become illegal" unit? For lending purposes, I know this would be considered a legal 3-unit.
On a similar note, does the Revised ADU Ordinance that just passed allow properties in the pilot areas to add legal conforming unit(s)? In my 3-unit with un-zoned/un-permitted basement example, would getting permits to rebuild the basement as an ADU add a "legal conforming unit"?
Hopefully this helps me and others understand how to optimize a properties potential. Thanks.