At this point, I'm thinking I'd like to invest in multiple properties - some for appreciation as a retirement nest egg and some for cash flow for now. 

The tenants we accepted continue to pay rent online through cozy.co .The tenants that we chose have been great so far, the only complaints really being the heat situation, since there is only one thermostat(I use a nest thermostat, which I can control max and min temps) bottom tenant likes it really hot, and upstairs not so much.

They had a nice nest-egg when they got out, 4 years later. 

Sure, many are living with their parents longer, but eventually, they must leave the nest and find their own place.

Despite the small preventative maintenance and home owning surprises ( hornet nest, leaking AC, sink clogs) it's been pretty smooth sailing, and now I'm itching to get another property.

The goal was to build our nest egg with flips.

I didnt want to invest right away because I wanted to make sure to save up a nest and build up my income with a stable job before jumping right into real estate investing.

Dehumidifier install--I'll bet they really like that.So even if they are a put off by the timing they will be more comfortable.If it were mine and and only 1 rental, or only 1 or 2, the "Rental Experience" I want to offer in this instance would be to try to find a convenient time that works for both.No need to play Drill Sargent and make them feel their privacy has been violated in a SFH as long as the option to be flexible is there.But, if you have no other option, then you have no other option.I'd let them scurry to clean the place for the visit (dust, pick up old crushed beer cans, empty ash trays (and hide them), wash the dishes, make the beds, move secret pets somewhere, etc....Turns are expensive, why step  on a Hornets nest if you have another option.An apartment complex is different, those run on a schedule, home or not, dryer vents get cleaned, washer hoses replaced, filters replaced, leaks fixed, etc...Just my 2 cents.

This will be the best way to build a large retirement nest egg without taking a lot of your time.

A lot of people are getting into real estate thinking that they will let a renter pay down their mortgage and at some point down the road through the magic of appreciation and full title, they will have a great nest egg.