A strip mall in the right location can be a real sweet investment. To get started, I'd probably hook up with a good design build contractor and pay them to do some conceptual layouts, cost budgeting and code review. I've built a few, one owned by a friend. That thing has been putting money in his pocket for about 25 years now.
Typically the landlord provides the "vanilla box" which is just a big open space with; ceiling with lights, basic heat & AC, a mechanical room and restroom in the back. The tenant then does all of the build out work, flooring, interior finishes, merchandising displays, counters, signs, etc. Separate utility services for each unit, and those are paid by tenant. Landlord takes care of building exterior, parking lot, landscaping, snow removal, roof, etc.