For pay-or-quits consider email and mail only, not in-persons unless you're leaning towards opening unlawful detainer. 

You'll want to file an unlawful detainer form.

This starts the legal clock.File for Eviction (Unlawful Detainer): If they don’t pay or leave by the notice deadline (often 3-14 days), file eviction papers with your local court immediately.Attend the Hearing: Courts prioritize these cases.

If the client had unlawful criteria (no kids, no criminal record, no section 8 source of income-whatever) then your job is to inform the client of the illegality and refuse to take him on as a client until he removes the illegal criteria. 

But I also do not do things like disposing of tenant possessions or other items that can result in getting sued (I.e. unlawful rent increases, illegal deposit with holding, not meeting basic housing requirements, illegal evictions, etc).Even with me abiding by the rules, I get threatened for law suit regularly.  

In many jurisdictions (Washington, Oregon, California & others) it is unlawful to contact people in foreclosure unless you are an attorney or real estate agent or loan officer .8.

In many jurisdictions (Washington, Oregon, California & others) it is unlawful to contact people in foreclosure unless you are an attorney or real estate agent or loan officer .8.

It shall be unlawful for any shared housing host to advertise for rental, list on any platform, rent or book for future rental any shared housing unit that is located in a building containing two to four dwelling units, inclusive, unless such dwelling unit is: (i) the shared housing host's primary residence, and (ii) is the only dwelling unit in the building that is or will be used as a shared housing unit or vacation rental, in any combination.

Landlord, you are filing for Unlawful detainger because the tenant owes you back rent. 

As this was getting complex, we continued with eviction steps and served Unlawful Detainer (UD) summons.