Foreclosed home: unknown residents

[Helen Mulu]

Purchased a foreclosed home in an auction, the home is occupied. I do not know if the home is occupied by renters ( which is likely) or previous owners. What is the best way of knowing the names of residents to serve them a notice? Other than knocking and asking for their names. 

I would like to approach them to come to agreement before Proceeding with eviction. What’s the best way of approaching them? If I give them sometime to move out on their own, how long would be acceptable? Considering I’m paying for internet daily and need access to the home ASAP.

thanks for your help.