A steel fabrication tenant will need to comply with runoff of cleaning materials and heavy metals, safety issues with welding gases, OSHA requirements applicable to the structure (safety rails, overhead beam loads that are part of the building structure and used for cranes and lifts).

@Ben Smith Following are the similarities and differences between the solo 401k and the self-directed IRA.The Self-Directed IRA and Solo 401k Similarities Both were created by congress for individuals to save for retirement;Both may be invested in alternative investments such as real estate, precious metals tax liens, promissory notes, private company shares, and stocks and mutual funds, to name a few;Both allow for Roth contributions;Both are subject to prohibited transaction rules;Both are subject to federal taxes at time of distribution;Both allow for checkbook control for placing alternative investments;Both may be invested in annuities;Both are protected from creditors;Both allow for nondeductible contributions;Both are prohibited from investing in assets listed under I.R.C. 408(m); andNeither may be invested in your own business.

The others seem to have recently been renovated with hardy siding, commercial carpet throughout or laminate flooring, new paint, and metal roofs (for some).

Much better then those cheap metal rings pex uses.

Go with your basic, no frills variety - top freezer, NO ice maker, metal wire shelves and fairly indestructible. 

@Robert Fisher metal roof you could possibly do yourself, better designs.

Many/most municipalities categorize them the group. ie, when you look it up it will say mobile/manufactured for the type of structure.In my case, the tax valuation on the property is ridiculously low and the Zillow value is also about half of what I think it's worth.A modular home is very different from a mobile home/manufactured home/house trailer, etc. ie, they're not on a metal frame, don't have that mobile home look with battens every four feet on the walls and ceilings, etc. and in my opinion are as good or better than most stick built homes.

Home Depot sells a nice black metal post that has screw holes in it.

You CAN'T rob the person of their possession, you CAN"T coerce them to give it up against their will, you CAN'T willfully deceive them (lie to owner of a gold jewelry that you are an expert in jewelry and that their item is made of cheap metal, and etc.).

There is very little a plumber could do to injuring himself or create a serious liability in terms of bodily injury to a homeowner or tenant (liability for property damage is a risk I'm often willing to take).As for electrical and HVAC, I nearly always want to have someone licensed and insured, as the liability is MUCH higher.