At least here in SoFla.If a unit is essentially for 2 ppl or the price per square foot is at a premium (NYC, SF, LA, etc.) then fine.

Example, price per overall square foot, kitchens X, baths y, flooring Z. 

The cost to refinish the hardwood floors (sand, stain and 3 coats of poly) is $2.50 per square foot.

And it escalates.Whether she's unstable, or a small misunderstanding lead to you two getting off on the wrong foot, the resolution at this point seems very clear to me. 

Junk cars, a junk boat, an RV, loads of foot traffic, and an off-leash dog.

I've got one foot on the airplane already.

Typical cost is $1/sq foot for maintenance (recoat and remediation) and $2/sq foot for a refoam.

Milwaukee may be a great option to get started, esp since you have family / foot on the ground there.  

Gah, you're definitely right about putting your foot down, but you can empathize with me about putting a foot down with a sweet old lady...

However, we are mostly using Converted Shipping Containers for a fraction of the cost, and they are built to last much longer than your Home Depot "shed" Depending upon the type of portable units you choose, the cost per square foot will vary Greatly, and delivery charges.