Having rentals that just pay for themselves or generate excess cashflow you can tap for other things?

The people are a bit abrasive and the fees are excessive.

Without evidence, it's hard to say.First, you should educate all of your tenants to report excessive noise to the police.

The guests have a credit card on file and your policy should allow you to charge for damages or excessive cleaning.

I personally don't charge for small holes and touch-ups unless they are grossly excessive, but I would charge for removing the tape/adhesive.

I have never held a mortgage 15 years (or even 12.5 years) and I have had quite a few mortgages.I claim that it is better to have the negative cash flow and use the $450k to achieve a return in excess of the 6%.  

Any excess proceeds not applied to the investment portion may be taxable as "boot."

I like to look for board orders, excessive fines for weeds/grass, stop orders, and unsecured premises. 

A good rule of thumb is to keep 3-6 months of operating expenses in your rental account as a cushion.Once you’ve got that covered, you can start investing the excess.

Can stay in the same budget and use the excess to invest or trade up.