The concept of an ADU is that it is an accessory dwelling on the Same lot as an existing home. 

Some cities in Canada have this strange rule where they do not allow accessory unit to be larger than 40% of total floor area. 

If you can't even tell how many units a property is really supposed to have by doing a walkthrough, I would guess that the construction quality is not very good.Here's some guidance on how accessory units (to an SFR) would be viewed.  

My husband and I submitted an offer on a single family house with an accessory dwelling unit studio in outer Los Angeles area.

Worse case scenario you have to rent somewhere short term until you start the job.I would highly recommend looking at a duplex or a single family with an accessory dwelling unit to give you more cashflow and more options down the road too.

Some towns allow such apartments as an accessory use.

Ballpark is $50k for the addition, and expected rent is $850.My home in SLC is luckily in a zone where accessory dwelling units are allowed.

2) Sounds like there are 2 legal, conforming units and then a grand-fathered/accessory garden unit where you would live?  

Portland area folks - I'd like to know if any of you have any first hand experience with Accessory Dwelling Units.  

#2, have you thought about building an accessory unit (small "granny" house) in the back, living back there, and renting out the main house?