Your scenario also assumes the property is paid off and that there is a lot of nontaxable proceeds from the sale to invest.

Doesn't seem right to me, but I can't find any definitive information anywhere else online.

@Ana Vhan, 1. like @Bill Brandt said you must purchase at least as much as your net sale ($920K) and use all of your proceeds ($520K) in your purchase or purchases. 

A business does not base their business plan on possible RE appreciation and sale of that building.

On loopnet there is a school for sale.  27,020 sq ft.  4,950 sqft gym.  5.8 acres

Talking to their sales rep, we had 25 applicants the first week it was listed.

Yes you should easily shed a good portion of it but to shed all of it will be a lot harder and needs diet and exercise (not just one)This is evident also by the latest treasury bond sales - other countries are slowing down buying our debt which means rates (especially mortgage rates (will stay higher longer).

The bank can call the loan due (due on sale cause).2.

I use online apps (Wave is one good one) have a separate bank account and separate ledger account for each property...

Also, many duplexes that i see for sale already have tenants.