It was a bit uncomfortable having the owner tell the tenants I was there to do an inspection of their apartments.

I have not had issues otherwise and a routine mid lease inspection was unremarkable.That Sunday I was working.

If you would feel uncomfortable having your grandparent going down the steps -- why would you buy it to begin with?

THE SECOND MONTH Somehow during the Second Month, when the newness wears off and the happiness falls into a routine, the new Tenants become confused.

Our clients routinely cash flow $500-$1,000 a month net of our management fees on simple single-family residences.  

I routinely do FHA loans for 3-4 units. 

I'm under contract to buy the house for 210,000, figure the arv would be 275,000, if I just go in and do my normal routine. 

If you have a quad built in the 50s or 60s, the routine expenses to make sure their is no deferred maintenance will be much different than for newer (not necessarily new) construction.

You just fall into a routine.

In that case while they were initially apprehensive all the tenants agreed to sign new MtM rental agreements (I told them I was not re-screening anybody, they would remain MtM,  and I laid out clearly what rent increases were coming the next 2 years)It sounds like you have been at least tangentially aware/involved in operating rentals for a while,  but if you are at all uncomfortable with the prospect of managing tenants and the occasional need to be firm or make hard decisions,  hire a property management firm.