They partnered with an experienced realtor who handled most of the contractor coordination while they focused on financing and design decisions..

Maybe a contractor whose income varies. 

Build a solid team, analyze deals quickly, and network with local agents, lenders, and contractors.

Insurance is expensive, there is a lot of extra maintenance like painting or electric in common areas that don't apply as much with smaller units. 

@Dani Murai, while I can't give you a name of anyone in your area (I am not from there), when you are interviewing contractors, here are a couple things I have seen:I avoid any contractor that has a draw schedule based on percentages, i.e. 1/3 up front, 1/3 at halfway completed and 1/3 at completion.  

For example: Landlord will pay for electric, water and sewer charges up to $100 per month.

However, exploring out of state markets could offer stronger cash flow upfront, so it’s worth evaluating both paths.A piece of advice would be to focus on building your core 4  team: agent, lender, contractor, and property manager.

For now, staying local allows me to leverage my property management experience—most of which came from working directly for family and close business associates who were property managers, contractors, and business owners.

It's not realistic in most cases because warehouses are built as that, which means they run much less electric and plumbing.

Quote from @Sam Brock: I'm a contractor and currently building two houses on two lots that I own outright.