Due to our particular circumstances (including our ages: late 60s), it would be difficult to get a conventional loan to leverage it, and buy more properties. 

With that said:If you're looking to stay in that particular area, it's probably going to be tough to find a property that fits both your needs/wants as a homeowner and the numbers that would make it work as an investment once you move on.  3bd/2ba in that part of town seem to be running well over $500k. 

Close to $0 taxes with a $500k net income from non-RE business?

All my properties are grandfathered in to the non-conforming zoning.  

When you say you want to put 20% down...do you have a particular purchase price in mind?

My home inspector contract says he is basically just a guy walking through the property looking for issues with no particular expertise (paraphrased). 

Our contract has a due diligence clause in it, so we can still back out if anything huge comes up.Current Home Info: 1970 sqft, 15 year mortgage (about 13.5 years left) at 3.375%, monthly payment of $1,241 (will go up a couple hundred due to SC taxes raising for non-primary residencies). 

The safe harbor applies to amounts paid during the tax year to acquire or produce what the regs call a “unit of property” (UOP), you must meet these requirements: (1) at the beginning of the tax year, the taxpayer has written accounting procedures treating as an expense for non-tax purposes amounts paid for property costing less than a specified dollar amount (which will be 2500 for you), or with an economic useful life of 12 months or less;.(2) the taxpayer treats the amount paid for the property as an expense on its books and records in accordance with its accounting procedures. ( do this on your bookkeeping software or whatever you utilize)(3) the amount paid for the UOP doesn't exceed $2,500. as substantiated by invoice.Note: The cost for the Unit of Property includes additional costs (for example, delivery fees, installation services, or similar costs) if these additional costs are included on the same invoice with the tangible property.Eg:A purchases 100 printers at $500 each for a total cost of $500,000 as indicated by the invoice.

I would ask him to get a preapproval for non-owner occupied mortgage.

They dig in to understand all the variables at play and why they should run a particular play at a particular time.