It was our first house and me and my wife bought and new it was a great investment that would work with college rentals and younger families.

If you have a 2-family that has a 1-bedroom unit and a 4-bedroom unit, you live in the smaller one and rent the bigger one.

I'm looking for a way to free up my time and invest to give my family a better life.

I am most likely going to start purchasing small multifamily/single-family homes in the Tri-Cities TN area this year.

This is a 2 family and the tenant on the second floor is having problems using the yard because my first floor tenant thinks the property belong to him.

He sure needs it.One option is to get family contact info and keep calling once you have it.   

My understanding is that assuming that one has no debt other than the mortgage for the first househack, it is calculated as(PITI1 + PITI2) / (Monthly Paycheck + 0.75*Rent1 + 0.75*Rent2)Rent1 is the total rent collected from the first property assuming that you have moved out and have fully rented it, and Rent2 is the rent collected from the other units in the new multi-family property that you want to buy.Is this correct?

For those that had SFRs and sold to buy a multi-family, when did you feel it was the right time to scale?

Great question....my answer is total guess vs expert response, but I don't think you probably gain much if anything by doing a cost seg on a single family house with long term renter. 

I have seen similar in some suburbs such as Waukegan, there apartment rentals are going for the price entire single family rentals went at few years ago.