Either1) your startup takes off and you can distribute profit fast enough to pay off your debts, or2) you find another source of $100,000 a year (which barely even starts to pay down the $300k, but might provide a better chance for a better loan), or3) you BK and possibly lose the rental houses to creditors (hopefully not, but we don’t know how they are held), or 4) you sell the houses, take the tax hit, work with the IRS on a payment plan whose interest will be much lower than your CCs, and focus on the startup.  

There are some areas near Gatlinburg I would consider, but cities are just a large HOA which I do not trust over the longterm.

There best move would be to put the property in a trust and not sell it until after the current homeowner passes away as that may allow the daughter to get a step up and then sell.Also, seller financing does not always net the highest price - and there is the issue of the seller having now to hope a loan does not go into default. 

I advise you to go personally and/or find a trusted local person.

I haven't heard of the bi-weekly credit card payment idea.

Then you can talk to the mortgage company or payment processor yourself. 

I know them well, I like them, and I trust them.My wife and I have purchased a wide range assets from PPR.  

Believing there is less risk because you are investing a small amount of money (in this case using only a 5% down payment) is the second biggest mistake you are making behind purchasing this asset property in the first place. 

I understand that if I rent this ADU out, then I can have a tax write off on the mortgage payment and insurance payment for the the ADU's sqft portion.

However, understanding their requirements—such as down payment percentages, reserve requirements, and loan-to-value ratios—is key to getting approved.One of the biggest advantages of working with portfolio lenders is their ability to fund deals that traditional banks might pass on.