These include Owners with Low Financial Stability Scores (FSS) and Seniors with Long-Time Ownership.The list broker will also be able to add phones and email to the list where available.Once you have the list, there are quite a few mail houses that have choices of templated letters and post cards.

and can I get a mortgage or loan for investing in U.S without being a citizen there?

US Citizen?

I tried this once with an older tenant feeling that a senior would be a great long term bet.

They showed me the income documentation. should I use the same application for us citizens?

When you have seniors on a fixed income, they may not be able to afford to do maintenance.

If you were to win the auction, in most places you would own the property, but only until the more senior liens foreclose.

I'm a physician (with stable W2 income higher than yours) and my spouse was Senior enlisted military when we went to buy our house (with a lower monthly mortgage than yours) in 2012.  

For the potential bidder at sale, the need to understand how to efficiently research title for loan position, senior liens, and condition of title when loan recorded becomes critical.The other obvious is is that a potential bidder does not normally have access to inspect the interior of the property being sold unless an owner-in-foreclosure cooperates (rare) or the property is vacant and entry is easy (I.e., breached door lock, etc.). 

Junior or Senior?