I want to build a detached ADU on my primary residence.

[Cindy Tansin]

Any recommendations?  Any experience with the kits that are built onsite?

[Tanya Solomon]

In 2020 I got the first "tiny house" -212 sq ft home on wheels that could be hooked up to utilities, put on a foundation, etc. legalized as an ADU in San Mateo CO. The home and area I did it in is around $800 per sq ft, so even with such a small home, I was able to make money. I bought the tiny home for $65,000 and then spent another $50,000 to install it.

The ADU laws in CA are VERY powerful. The state is trying to encourage ppl to create these in the hope that it will provide "affordable housing." Per CA ADU guide here https://www.hcd.ca.gov/sites/d...
15) Ministerially Approved ADUs and Junior ADUs (JADUs) Not
Subject to Local Standards

Check out the State law before approaching your local county. Local counties can be a bear to deal with on ADUs. They are being forced to approve them by that State bc State laws and policies trump local. San Mateo is terrible as the building and planning dept are both maleficent and incompetent but persistence paid off. Neighbors can complain but they can not block you as long as you fulfill the requirements, which is nice. Ppl can be NIMBY pains sometimes and want to dictate what you do with your own land. 

Here is another helpful site https://www.hcd.ca.gov/accessory-dwelling-units#:~:text=New%20ADU%20funding%20laws%20effective,low%20to%20moderate%2Dincome%20households.

Things to keep in mind:

-If you go prebuilt, you want to buy something built to code for your county. You will need blueprints, a site map showing where the main house is and that the set backs are all kosher, and even title 24 (energy code and conservation stuff), at least. My plans for the tiny house/adu were a whooping 11 pages long! 

-They now allow two, so be strategic and if two could fit, do one now and then maybe another down the road? 

-I 100% agree with @Paul Dashevsky that "usually" (I would say ALWAYS) "still need someone (a local contractor) to build a foundation, run utilities (water, sewer, electricity, gas) to the ADU, and build out any other necessary site-work: landscaping, patio/driveway, fencing, etc. Dont forget to budget for this when you're considering an a ADU kit" This is absolutely true

I am so excited for you bc the law and policies in CA have made this process so much easier and cheaper. Keep in mind anything worth doing is work and this is true in regards to ADUs. They are work, money and time but MUCH easier than stick building or otherwise a primary residence. They are a great way to add equity relatively fast 

Id be happy to answer any questions about my experience if ppl want to ask