First, I would get with two people, an investing friendly real estate agent which you could connect with on here as well as a local lender.

They wont have it either and they won't have their CDC guidelines or excuses.   

The underwriter of your loan may want to see your current property be leased and make sure that it covers your PITI, but that will depend on the guidelines of your lender.

Thanks so much for your help in advance I would see if you could do a rent to own or seller finance. you are going to have trouble getting financing without income for a primary residence as the lender has to follow federal guidelines and your ability to repay - which if you do not have income that makes it challenging to qualify. 

They'll have to find a home they can afford, and then one that meets the guidelines (needs to be in good condition.) 

The kids can always go to a friend's house while you're there.I'd also look at when her lease is up for renewal and tell her you are not renewing her lease and she needs to find another place to live.

There are turnkey companies or platforms like Roofstock that assist investors in doing so or you can contact property management companies or look for investor friendly real estate agents in that market to assist you.  

I was asked yesterday by a good friend of mine who has got 1-2 rentals in the last year and I wanted to check with you all first.

I’m looking to team up with two friends who are eager to move out of their parents’ homes.

San Diego and the surrounding areas are VERY ADU friendly so there are properties with options to add one in the back that are really starting to pop there and could be an alternative option.Take it slow.