Squatter won’t pay rent!

[Charles A.]

So I inherited a squatter at closing. He was listed as “boyfriend” of previous tenant on lease I inherited from seller. Problem is that lease expired May 2018. The original tenant on the lease moved out on expiration of lease and i never met her. Now this boyfriend is late on rent. He’s technically not on lease. I’m planning to ask my agent to post a 3-day notice on Monday. But I’m not sure that even applies as technically he’s not my tenant as he never signed a lease. Has anyone dealt with this situation?