Finding specific off market properties

[Audrey Blotz]

New investor here looking for some advice - I've realized that my ideal property is a home with some type of ADU so that I can rent out the main house long-term and use the ADU for short/midterm rental.

I recently listened to a real estate rookie podcast in which the new investor was looking for a similar property and mailed out letters to specific properties in a specific neighborhood in order to find off market deals. 

How can I find a list of homes that are not currently for sale but that may have an ADU, so that I can start to reach out to these owners about any potential interest in selling? Is this possible?

Thank you all! 

Audrey