Take ownership of your mistake and learn to do the proper due diligence recommended above😊

They need to do all their due diligence including understanding the value that will be added by the ADU, the finance options available, the consequences of adding the ADU (rent control, property taxes, rental limitations, etc), etc.Good luck

That market from what I can see on the few trips I made to perform due diligence is really robust and such a pretty area I can see the attraction for those working in Tech or govmit in DC. 

Talk about not doing your due diligence!

The three ways to handle the risk are (1) gaining knowledge and experience in both investment in general and in the area you’re investing in specifically (2) extensive due diligence and when the inevitable bad outcomes occur despite (1) and (2) then (3) diversification.  

Don't let a great deal cloud your judgement - do your due diligence first!

Just do your due diligence and be aware of what’s going on.

Quote from @Adam Bartomeo: Sounds like someone didn't read their contract and do their due diligence.

If you're just looking to fund a handful of deals a year you  may be OK (consult an attorney) but definitely do your due diligence.  

Pick one strategy and master the due diligence side of it.Another thing to keep in mind is how much capital you have, and how many properties you want to acquire.