My question in the class was, how they define “investment” in the property, if they refer to just the mortgage principal, or if it includes any improvements done inside the unit. 

You could start a new company and find a broker, or someone easily licensed, like a NYS attorney, to partner with to be the principal broker for the organization.  

@Mathew Scott It really depends, nothing wrong with leverage as long as it makes sense numbers wise.If you like the numbers when principal pay down is factored in, than the deal may work for you.

I did find one bank that would refinance to a 15-year loan at a good rate, but that would involve throwing a lot of cash into principal to get the payment down to the point it keeps cashflowing strongly.I've only ever bought two places, this rental and the one I'm in now, but I had considered buying a 3rd place in DC before my next overseas stint. 

Focus on principal pay-down & leverage 1st.

They paid the bills but I didn't make much/anything other than paying down a bit of principal.

Pay the beneficiary the principal sum of $_______________________________ plus interest at____________________% per annum from _________________________, 20_____ to the date of closeof escrow;2.

You need to be disciplined to pay part of the principal too.Many people use a HELOC to make fast "cash" offers on properties, then refinance the balance from the HELOC into a mortgage on the property.

I was making in excess of $150,000 annually without going out the door and with no reduction of principal.

Yeah, you will pay more interest over the course of the loan because of the higher principal amount.