Which agency is responsible for evicting Trump  if he's impeached, removed from office yet refuses to go?

Probably the Secret Service since they would have to secure the White House for Trump's successor.

The Secret Servise might escort him and his people out before the fumigators and pest control come in.  The the place will have to be de-bugged from when the Russians met with Trump alone.  

Dunno.  What agency evicts folks from public housing?

There is a 0.00% chance the Republican controlled Senate will remove him from office. The House impeaches him but that only starts a trial that is conducted in the Senate by the Senate and the vote to remove him is done by the Senate. Trump isn't going anywhere chum

white house guards 

Send in the SEALS.

Trump has sacrificed his standard of living to be President . The White House is like Motel 6 for the Trumps .

He is only there because it's part of his duty as President .

Unlike the 0bamas that were left homeless when they lost their public housing .

Police probably

maybe the police