In the bigger firms, one usually has to "earn" this coveted honor.

Original terrazzo in good shape is extremely expensive and very coveted, especially in mid century modern homes -- which are in great demand and growing.

@Alek LupaWhile there are always folks who will live in a basement, this type of accessory apartment is generally less desirable than an above ground unit.In addition, digging down a crawlspace and underpinning the foundation is an expensive undertaking (provided it is possible, sometimes houses have crawlspaces, rather than a basement for reasons other than economics).  

Account Closed I would read into the local rules on Accessory Dwelling Units it may not be exactly your goal but a lot of cities with housing shortages allow ADUs aka In-law units to help alleviate housing shortages.  

One thing to look into it to see if you can put an accessory structure.

Most the info came from the county accessory website that is already free.

If you work backwards and start to locate properties that have your clients' coveted ROI they can't argue price with you. 

We used the proceeds to  add an accessory dwelling unit. 

Heres the deal: Field Card info: "Unique two family with an accessory apartment.

Over the course of a two years or, you're sitting on a 3-5 home portfolioOf course, multi-family properties are at a premium, and if you find a deal you may not be in the most desirable neighborhood, but rents are high even for modest accommodation.One very nice development specific to San Diego right now is how relaxed the zoning laws have become with regard to Accessory Dwelling Units (ADU's).