Supplementing with flips, new construction or some other form of REI, keeps the interest there and actually pays the bills without having to use your cash flow to live and hence, killing the golden goose.

I rented both sides of the duplex and was supplementing my income nicely.

Why would you choose to supplement your tenants rent.

I don't need a huge passive income currently, but I do hope to build up my portfolio in the years to come to increase my net worth and maybe have supplemental income down the road. 

We have to make sure that the operator has strong supplemental STR liability insurance EVERY YEAR.From an operator perspective:You don't own anything (except the furniture).

(We did opt to get some supplemental landlord insurance for a mere $300/yr. just for added protection.)

It is supplemental income, for her and she is not going to make major repairs. 

What if I need supplemental income when I retire?

I am exploring the idea if turning this into a part time STR is a good idea even if it is only supplemental income to defer some costs of the mortgage.

You have a full time job so I'm assuming you don't need the cash flow to supplement your income.