I was buying homes for $100k with $25k of my money, and the mortgage was paid off by the tenants.

Most mortgage companies will not call loan due if payments are current but you do run that risk and need to be prepared to payoff or refi at a moments notice.

I can tell it is not common to negotiate because the realtors I am working with know that in the past, I used a realtor who charges less (and also gives less than great customer service), and they keep telling me how bad she is and that you cannot give proper customer service when she plays the volume game.

I continue making the underlying mortgage payment myself (autopay) and get reimbursed from the borrowers payment.

Research ways to use your education to help you qualify for a loan (did you know that some lenders allow college credits that translate directly to the line of work the graduate pursues to count towards work experience, accelerating the borrower's opportunity to get approved for a mortgage?). 

Thank you Brett, mainly for properly reading my inquiry and genuinely trying to help me.

And your bank is not requiring any sort of paydown of the mortgage for a partial release. 

Our company Nationwide Mortgage Licensing System & Registry (NMLS) ID number is 1553947.

$6000 is a large mortgage to cover for a vacancy. 

I flipped two my first year and made a great profit $70,000+(2021), I had zero land deals the next year (2022) I had two deals fall thru,  but used my knowledge and resources to get my family into a bigger/newer house ( using subject-to financing), sell my old house and payoff the sub-to mortgage and make $20,000 on top.