The other option is to build an addition with an ADU (accessory dwelling unit) finishing the house and adding another 650 sqft to the main house ( 3 bed 2 bath ) and a 550 sqft attached ADU (1 bed 1 bath). 

@Ed AllenMatt Lesher at The Agency PDX is a fantastic broker, and also an investor himself.Another idea you could look at is buying an SFR with an Accessory Dwelling Unit (ADU) on the property, which could be detached or within the main house i.e. basement as you said.

This was to be my forever home with an accessory unit on the property.

The in-law unit is a legal Accessory Unit.  

In certain zoning districts the city will allow an accessory structure as long as it doesn't have a kitchen.

I just put an offer on a 1100sqft 3/2 SFR on a half acre.  Should rent for $1000-$1200.  Was wondering if putting a pre-fab storage building in the back yard might allow me to charge an extra $100 or so.  Any opinions...

I'm targeting Asheville properties with accessory dwelling units or in-law suites/basements to AirBnb out.Here's my question.  

I've been running the numbers on adding and ADU on to my primary residence. My goal is to add on to my section of the house and have the rental income from the ADU cover the cost of the project.  Does anyone have any ...

I don't normally consider investing in single family homes but this new zoning law just made them valuable, especially if an accessory structor already exists.

Look up your local rules on in-law units also known as accessory dwelling units.