Give the cost of money these days is around 7%, it would definitely be nice to have a paid off rental.Like Tim said, the 7% is largely irrelevant because your tenants are paying it with the exception of vacancy periods. 

Is it a big hassle to add the extra money at the end of each year, or whatever the reinvestment period is?

The Earnest Money Deposit (EMD) is refundable during the Due Diligence (inspection) period, and goes hard at the expiration of the DD period.

The more you pay upfront the lower the rate, but you have to make sure to do the math on what you payback period will be.

My Mom's family grew up with two generations of the local family get togethers and knowing all the extended cousins, so did my wife's family.

Or at least just getting all of your thoughts and numbers on paper (or in a spreadsheet) and mapped out over the time period you're talking about, I think would be a very helpful exercise for you.

There is nothing that says you can't be under contract to sell within or before your 45 day identification period even begins.

If you’re running a MTR more like a STR, then you can decide to charge the full boat as agreed or, if you desire (possibly to obtain a good review) find a substitute renter for the period in question and credit the original renter.If, like me you operate a MTR more like a LTR just for a shorter period of time, you probably use a specific rental form provided by either the state real estate commission of the local NAR affiliate.  

Thank you Steven, if your HML will not extend for you, I would recommend a 0yr PPP DSCR loan.

Extend closing and have the condition of the sale that the seller provides the unit vacant.