In my case, I have residential rentals in one LLC, commercial properties in another, self storage in a third, and my real estate company operates in a fourth.

The property we bought around $475,000 at the time (paying 25% down) and in 13 years is now over USD$1.1million (our neighbor upstairs and comps are selling for that and our apartment is nicer and has more things...like a wine cellar, full parking spot and 'bodega' (storage) in the middle of city, storage, winter garden, etc.).

Added a coin operated washer and dryer, turned half of the basement into a storage unit which leases for $100 a month.

I'm a commercial lender with many multi-family properties financed, and I also have my own portfolio of storage facilities.

My commercial broker suggested I look into other types of commercial real estate assets such as office, retail, mobile homes, storage, …etc.

If the entity produces passive income such as rentals or interest, then there is no generation of Unrelated Business Taxable Income.If, however, the entity is engaging in a services business or something similar, perhaps hotels, self-storage, adult care, etc., then that produces trade or business income.  

Commercials properties, lease options, single fam, multi f, storage unit, whole life insurance (be your own bank), small business(ice cream shop), airbnb,etc...

“The gross building areais the total finished area including any interior common areas, such as stairways and hallways of the improvements based on exterior measurements;is the most common comparison for two- to four-unit properties;must be consistently developed for the subject property and all comparables used in the appraisal;must include all finished above-grade and below-grade living areas, counting all interior common areas such as stairways, hallways, storage rooms; andcannot count exterior common areas, such as open stairways.Fannie Mae will accept the use of other comparisons for two- to four-unit properties, such as the total above-grade and below-grade areas discussed in Gross Living Area, provided the appraiserexplains the reasons he or she did not use a gross building area comparison, andclearly describes the comparisons that were made.”The actual form utilized, in this case Form 1025, does not in any way dictate what is proper and appropriate in the completion and reporting of the appraisal.

I recently had a tenant put a charcoal grill in their attached storage closet with hot coals still present - which ofcourse resulted in carbon monoxide filling the closet, and then the house.

Or a self storage facility with an owners quarters.