Question on the ARM, is there a negative to making extra payments to the principal?

Your goal is to build equity, which can be done through several ways (cash flow, appreciation, principal paydown, tax shielding, etc).

All that is due is your principal balance.

In addition to the $75k "cash flow" you mention i assume you're making principal payments on the debt which also records in the profit column at the end of the year.

On principal, I am against "generational wealth".

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable). 

You will then have a few options with that rent money....you can put it into principal or you can start saving it to purchase yet another property.

If you search these forums you will find countless syndication investors burned by paused redemptions, loss of most or all of their principal, investment promoters disappearing, etc.

I calculate principal pay down on the mortgage over a period of time.

If you're applying for a Conventional/FHA/VA/ or USDA loan, then they will do a "global cash flow" where they take into account your PITI (Principal + Interest + Taxes + Insurance (hazard and flood) on all properties (second mortgages included), HOA payments, car payments, student loan payments, credit card payments, and installment loan payments in the numerator and your gross income in the denominator.