Could be related to misreported accounts, credit report errors, identity theft, divorce that included joint accounts, or even legitimate accounts that had been settled or could be paid off quickly.We've had terrific long term tenants who messed up their credit history and were forced to become long-term renters since they would never qualify for a home mortgage. 

Are there any other ways to feel relatively safe you will not be hit with a big unknown lien once you buy?

This positive experience has turned me onto real estate and other related opportunities.

Please feel free to share your experience and input, I am sure some investors will relate to these pesky little concerns.

This will vary widely from market to market, depending on Zillow's access to market data. 

I know this because we sat down and looked at her credit report in the Mint app (a soft inquiry, and yes I know it only gives data from 1 agency but I don't expect the other 2 to be vastly different).

I am looking for buy and hold type income properties, and have created a relatively simple analyzer to screen potential options.

I am young and extremely new to this game so any responses related to becoming a landlord will be helpful!!

Will they be residents, are they relatives, etc.

You can use city-data to find owner occupied percentages for neighborhoods.