Hi Shelby To determine rental prices and demand in a neighborhood, start by researching comparable rentals in the area, focusing on properties of similar size, type, and amenities.

My brother lives above.3.  2007 house just updated by owner.4.  

The big issue is building a single small residential unit is the most expensive residential development.Here is a list of why adding a single ADU in single family zoned areas in my CA market is typically a poor RE investment:1) The value added by the ADU addition is often significantly less than the cost of adding the ADU.

Real estate has long been the foundation of lasting wealth, proven by historical and modern moguls alike.

By this logic investing in a new roof also doesn't make sense.

I rented to ACU students and used the rent by the room method.

Quote from @Brandon Robertson Quote from @Denise Evans: Do NOT sit by and let him build and then hit him up for a "better price."

So your additional ~240 SF could be the foyer, hallway and bathroom spaces that are allocated by percentage to the unit.

I don't remember exactly, but its on top of my 2-car garage, so 20 ft by 22 ft maybe?

I am seeing a trend in CA that ADU construction is more cost effective (per unit) than buying on the market by a long shot.