Wealth-drivers are appreciation, debt pay-down (ie. principal payments) and tax shielding.

If you are paying cash for the STR this seems pretty easy. 

The buyer may pay off the remaining balance at any time without penalty.2.

Throughout this entire time, I waited tables and bartended at night to pay rent.

I don't know your living situation but if your paying x,xxx for rent or a mortgage and instead by living in one side and renting out the other you will be paying y,yyy instead and y is less then x that's great, especially if you can rent out your primary residence and make income there too. 

Look for safe accounts that pay good interest or dividends to grow your security.

So, if you buy an older home it's typically much cheaper, since you're not paying much for the structure. 

We had an accounting system once that necessitated doing this - not ideal, but it keeps the assets and liabilities straight and AP is just an accrual until you pay the bill.

If you allow service dog, you sure need to pay a deposit , application fee and monthly pet rent correct?

Remember, someone else is paying off a chunk of that asset.