How can I find a list of homes that are not currently for sale but that may have an ADU, so that I can start to reach out to these owners about any potential interest in selling?

California is most definitely a Tax-deed sale state. 

A project will have a life cycle that spans close (purchase of distressed) to close (sale or refi at new value). 

Additionally, optimizing your online listings with high-quality photos, compelling descriptions, and virtual tours can boost interest.

As responsible Real Estate Investors,  we want to educate them on their options:  Mortgage relief programs, loan modifications, forbearance, short sale, etc. 

Can my sister and I donate land my deceased parents received deeds through in tax sales? 

Jack Bosch and a lot of the land flipper guys who teach it like to have their students buying in the high deserts and remote areas of the Western US  or in FLA like le High Acres etc. this is were cheap land is and land that gets traded constantly at tax sales.. the play for most of them is really simple.buy at tax sale or with direct mail.. for a few grand  re-market them for more and sell on terms and collect monthly payments.. 

Michelle,In the NYC market, i think our best search resource is Streeteasy, it's the most up to date and provides the most accurate historical sales data. 

Is there opportunity to put some money into your current home to increase the equity and sell (you would need to get more than $1 back in the sale for every $1 put into it)? 

@Dominick Tonnarini, The only issue with your plan is that you will have to pay a sizable tax on the sale of that property when you do sell.