Because it is a detached garage, known as an accessory building, adding a dwelling within would make the lot have two buildings/structures on it.

Needless to say, my first phone call would be to Denver Zoning.I spoke to denver zoning and the size of the ADU is relative to the lot and not the primary dwelling.

Single dwelling with smaller floor plans are 650-700K in 2016Property under contract 620KCity of OrangeDirectly across local university Zoned: R16000 sq ft3bd/1ba - 1500 sq ft main dwelling$2700 rent for main dwellingmain dwelling needs 50k of rehab on its ownallowed up to a 640 sqft accessory unit with an attached garage that does not count against 640 sq ft.public access way available to accessory unit garage$1800 potential rent for accessory unitHave at it BP. 

Any advance or deposit of money furnished by a tenant or lessee to a landlord or lessor to secure the performance of any part of a written or oral lease or rental agreement shall be returned to the tenant or lessee of residential or dwelling premises within one month after the lease shall terminate, except that the landlord or lessor may retain all or any portion of the advance or deposit which is reasonably necessary to remedy a default of the tenant or to remedy unreasonable wear to the premises.  

Don't expect the land to be cheap.The main thing that drives the price of residential properties (including multi-unit dwellings) is the location.Location, location, location!

The world of real estate is as varied as the investors that dwell in it. 

I am looking to buy a single family in Morris County NJ and want to zone it  as a two family dwelling.

In San Jose and per codes I’m allowed to build an accessory Dwelling unit in my backyard.

The converted apartment should be permitted and approved as a second dwelling.

You may have to get creative...find a duplex in a good area and Airbnb the units or find an SFR with a legal accessory dwelling unit and live in the smaller unit while renting out the main etc.