To me, having one mortgage payment for 2 - 4 houses (basically) always seemed interesting and like something that would give me more bang for my buck. 

I will give you my numbers since we are 3 years into Velocity Banking.Home was purchased at $410k.Interest rate: 3.125%30 year termMortgage payment is around $1950 (includes insurance and property tax)HELOC: 8.25% Variable rate - current rateCredit Limit: $97kLet's say I made $10k a month and our expenses were $6k each month including the mortgage.

Most lenders I work with would lend you 70%-75% of the value of the property, but only so much that your NOI/profit is 20%-25% of the monthly loan payment.

Don't accept ANY partial payments.

Like the previous poster mentioned, you would be buying into a payment.

Payments $492 (interest, tax, insurance) currently owe $51K.

Also go through a servicing company for payments to the seller, escrow can probably help you out with a recommendation for that. 

I forget; it was payment processing related) that required me to have a website for the business.

Your payment requirement would rule you out for us. 

Here’s a chart showing what percentage of an American’s average mortgage payment goes to taxes and insurance:Rising taxes and insurance premiums make real estate even less affordable for buyers already facing higher home prices and mortgage rates that rose ~150% in less than two years.