Welcome to BP, @Tom GuenzlerStay involved on the forums and check out the podcasts for tons of great insight into the real estate investing space.

They then leased out the other spaces.  

Example, we located a commercial property that could be purchased for 10 thousand the property is zoned mixed use it has 1 existing apartment that needs full rehab and could allow up to 4 apartments in the entire building and a large retail space.

There are three floors.

Then we will build a 10x10 room downstairs as well so turn it into a 3bed, 2bath place and add about 250 sq ft of space total. 

It needs walls, toilets, tubs, flooring, etc. 

Leaking toilet with ceiling repair needed, another leaking toilet with sub floor repair needed, some new windows needed, new AC needed, a bunch of small electrical work, some roof issues due to ice dams that needs to be fixed, asphalt and garage foundation repair, gutters needed (none).

Do you care more about space or cool location?

My most expensive rehab to date was $60K on a $350K house that I took down to the 2x4s on the inside, rearranged the entire floor plan, rewired with permits and added upgraded panel, new windows, re-plumbed, sheet rocked, and replastered the pool as well as added all new pool equipment and blew out the inside with the latest finishes.I just put a house back together that probably should have been scraped off the lot and it only cost $35K.

There's also companies that build "empty" towers and lease out tower space to a variety of other services (public safety, WISP, industry, etc.).