Rents are currently $1,200 per month, I expect to raise them to $1,375 per month when I add a storage container and do exterior fix ups (30k), the monthly payment is $3,660, so $5,500-$3,660=$1,840, so $22,080 cashflow per year.Summary:Utah is an increasingly expensive market.

Best case, I'd put an extra fridge, some plants, storage shelves, shoe racks, etc. 

does anyone have any experience with investing in self storage?

We kept the spaces at mobile home size dimensions and added storage sheds. 

Purchase price: $299,000 Cash invested: $310,000 28 Unit Self Storage Facility

Is it true when underwriting small storage facilities that you should use a high cap rate between 12% - 15%?

If they are smallish, perhaps an easier option is to create storage units in this unfinished apartment that the tenants can rent.

I have a neighbor with an odd sized little piece of property that would work for me to build a shop for woodworking and general storage.

Since current tenant still there, owner will have to pay for new tenant's housing in a hotel plus temp storage of their belongings, etc.

That will have to change or there will need to be a big fat disclosure from the listing agent that they are in no way representing the buyer even though they are writing the contract and handling all the inspections and such.