In-law quarter/ADU in Dublin CA worth to build?

[Manoj Lamba]

Is it worth to add rentable in-law quarter/ADU in Dublin CA (West Dublin) house, which costing ~85K or so to build for 300 sq. ft. built up area for the in-law quarter?

How much rent it would bring in and is it easily rentable?

Does it add value to property in the same amount as main house for per sq. ft. price or lesser? i.e. if house is being sold at $600/sq.ft., does the ADU too priced at the same value?