San Jose SFH RM zone or ADU

[Jim G.]

I am new on this. Need your input. I have a rental home in San Jose. SFH, 1 story 1500sf sits on 5650sf corner lot. The city record shows as RM zone, which means it is qualified as medium density zoning. What hurdle do I need to go through to convert it into a duplex? I plan still keep existing 1500sf house, how much addition can I add to reconfigure it into a duplex?

Another ADU route, which seems much easier to do, for not just RM lot, but in general R1 lot, which is ADU. Having checked the ADU code in San Jose, I can only add 600sf addition. I want to know pros and cons of duplex vs ADU, given the size of lots and existing house structure I gave above.