When a tenant moves out and new tenant moves in.

[John Chea]

Hello everyone,  I am new to property management, my tenants are grandfathered in when I bought the property and would like to know how I should handle the current situation.  Short story,  husband and wife on month to month separated, wife moved out, husband stayed and got 2 roommates.   What if anything should I be doing to protect myself?  I would appreciate any advice.