I learned always to have more than one financing plan.

Agreed, $50k~ does not go very far as a 20% downpayment in St Augustine lately, and although you mentioned you have a higher risk tolerance, that would be a lot of debt you would be undertaking between margin, your existing rental property debts, and the new debt with the planned purchase.

Tenant just informed me they plan to vacate the property tomorrow (so, 24 hours notice) due to "the business growing and the space now being too small for their needs."

I was planning on renting out the the living room as a bedroom.  

If you were buying a 2-4 unit in your personal name and planned on living in one side, you might be able to get 10% down financing.

It's worked great for us the past few years and I don't have any plans on changing systems.

I would love to get connected with more Brokers and lenders and tell them all about my plan.

So, maybe that’s what retirement is all about.Maybe you feel guilty for not doing more to plan for retirement, yet it’s so far in the future, and such a daunting task, that it’s always something to put off till tomorrow, or the weekend, or next year.

In our contracts, there’s a paragraph that says whether or not the buyer plans on living there as their primary residence, for insurance and tax reasons

I'd get an attorney ASAP who's on board with the following actions plan.