It's considered an accessory use to your primary residence, but when you move out -- again, technically, you're only allowed to rent the whole space to one party.)

Here is the Urban Growth Area Map.http://www.co.thurston.wa.us/planning/comp-plan/docs/M-14%20ugas%20for%20land%20use%20chapter%20gina.pdf Here is a quote from the Thurston Co. website:http://www.co.thurston.wa.us/permitting/faq/faq-aboutproperty.htm  Can I build an accessory dwelling unit or an accessory living quarters on my property?

There is an accessory dwelling unit, which I intend to rent out.

The code you cited states that accessory structures can't be rented out. 

Is it even worthwhile to build an accessory apartment? 

If Tenant smokes/vapes or allows others to smoke/vape on thepremises, Tenant agrees to pay a penalty fee of fifty dollars ($50) perviolation.

My wife bought several sets of furniture and accessories, each with a different color scheme.

I am beginning to think maybe some agents might consider such an accessory if they like to fly solo when doing business with strangers.

@Chad Clement Both accessory and principal require homestead exemption.

Here is the link to the Somerville proposed zoning changes: https://www.somervillezoning.com/If you read through everything carefully it basically looks like they are proposing that if you have a large enough lot size or enough frontage you can build an "accessory dwelling" behind your house.