This is a classic 1031 strategy called a diversification exchange.

I am renting a detached garage to someone that is not a tenant at the property- they are storing their classic car there and plan to keep it here for about a year while e builds a new garage at his house, will not be stopping by to take it out more than every few months.

The classic for self-flip, even when they are contractors, is it takes 2.5-3x longer than they think because a lot of time they are asking for "help" from their employees on weekends. 

It might even make more sense than the classic BRRRR, because as an owner-occupier of the property a mortgage lender will offer a higher loan to appraised value product, taking less cash out of your war chest and leaving you more cash for rehab. 

@Philip Liu  The classic rule is to buy based on actuals, not potential. 

She is a classic problem tenant.

It's a classic.

The purpose of the GST tax is to generate revenue from federal estate taxes; if a generation (child) is skipped by the transfer of wealth to a much younger person (the gift skips the child and goes directly to the grandchild), there will be no estate tax when the child dies because they did not own the transferred asset.A classic example of a GST involves a grandparent who transfers assets directly to a grandchild or to a trust established for a grandchild’s benefit.

The typical classic approach focuses on present median rents but it may be possible the big boys are projecting higher rents in the future and basing estimates on that. 

One last thing to keep in mind is that some buyers won’t want to pay as much for a modular build compared to classic construction.