Please Advise: ADU Cost Components Breakdown?

[Emil Pinlac]

Would anyone be able to give a quick breakdown of the various costs associated with planning and building an ADU in either your backyard, or as a garage-conversion in California? I'm talking about modest-sized JADUs or ADUs in the 400-600 sq. ft. range.

I've been considering building or converting a garage into these units, for a long-term, buy & hold real estate strategy. But I just wasn't sure where to start, or how to properly save/consider the various costs associated with them.