For less than $500K I am getting the following 2 Houses--3/2 mobile home - my family home -- 4/2 Metal home - Airbnb 1: similar properties average $6K/month.            2 separate garages ( one is ready to convert to extra master - has windows, insulation, and ready for paint)1 Shop - 1,200 sq ft metal building with electric, plumbing, and water -1 Shed with toilet - wellness spa ( I am licensed esthetician/massage therapy)3 - 600 sq. ft. 

Metal posts (the chain link type.Why not just tell them they have to pull a chain link fence (to code max height) and not have to replace the wood every so many years.The prickly top type will limit kids from jumping the fence and bending the horizontal bars.They want to fence off the lake view (???)

FWIW I've seen inspectors miss alot too, cracked heat exchanger & plugged fan coils in HVAC FAU.

Fixing leaks in a bathroom that was dripping into the downstairs unit's kitchen, fixing a leak in the roof, wrapping the windows' trim in metal, having new/working gutters installed.

I sold my home in Florida about 20 months ago and have been heavily vested in precious metals since.    

Put in a plumbed metal washer pan if you allow a washer, regardless of who provides the washer.Second item is verify the plumbed washer pan is plumbed correctly. 

What do you think if I do give her a lawnmower,  with a bike lock so she can lock it to the metal fence and make sure only she has a key/knows the code to unlock it.

The heat coils can address this.

New Lineset will be ran through attic and new coil will sit on existing furnace.

I would suggest the partition walls be framed out of metal building materials with metal panels on each side, so it would be easy to take down and store if a tenant wants a bigger area.Insulation wise, go with the standard metal building insulation on the roof and walls.