I profit a little over 3k a month after all the bills for the three houses are paid. 

I was thinking that they get paid the most when there is turnover, so has anyone been successful in crafting an agreement that rewards for:Tenant longevityShort vacancyKeeping repair costs down (I do want to address issues though)Dunno...

If going conventional route or agency route, Interest only for the first 1-3 years is available, esp with Agency financing, depending on term length, but you're still going to be locked into some type of pre-pay just because they are 30 year amortizing loans.

He finally paid the landlord for all that was due and the landlord stopped sending him Christmas cards.

Once you acquire, you start your rehab, let's say you upgrade the kitchen and it costs you $15k -- you submit your receipts to the lender to show you paid $15k for the kitchen, and they send someone out to verify the kitchen is done.

So the higher cash flow is the return on the full price of the property you paid in full for, whereas with leveraging, the lower cash flow is only in relation to how much you put down, which probably isn't much.

I am trying to acquire more properties for my portfolio, but the banks will not give me a pre-approval for a loan with any of my units vacant.

I am now questioning if my realtor has my best interest or just making sure my property rents and gets paid. 

You can find pre written forms on BP and google.

Depending on how long you plan on holding onto the the property, it may not even make sense.When I house-hacked, I just paid for the water.