I’ve been told that a 4 unit building is a good option for a first rental property.I‘m interested in any advice/warnings that you might give someone in my position.

There are tenants in one of the houses (I would owner occupy the other house) and when I went to tour the house my realtor warned me that they are usually awful to anyone who is trying to buy the property.

Allows landlord to not renew fixed term tenancy if tenant receives three lease violation warnings within 12 months during term and landlord gives 90 days’ notice. 

I do warn my tenants not to schedule the payments more than 10 days before the due date because, otherwise, Cozy will not recognize it as paid - one of the interface design flaws. 

I personally would warn this tenant that they are going to be evicted if they do not pay rent on time as per the agreement.

The manufacturer's warning placard on the water heater states that water temperature above 125 degrees F can cause burns from scalds and possibly death.

I sternly advised them to quickly address the matter, reminding them of their liability if the worst happens. 

I would further warn the young couple that they are gone if there’s smoking by them or a guest .

In other words, they were banking on future events they had little or no warning or control over.I have at least 25% equity in my properties, and at least enough cash flow to cover the "fall backs" in a down market.  

The warning signs were evident the moment they asked you what you had into it - which should have been COMPLETELY irrelevant, and I reckon you would have been best served by calling them out on that point, and so not told them your purchase AND rehab costs.