Charles, first clearly understanding the zoning codes and compliance is a first test, especially in mixed use properties. I was involved in the process of assessing the use of mixed use properties here and specific zoning might be applied and restrictive. Having a retail code with residential may not mean you can put in a resturant with a bar on the ground floor and apartments on upper levels. So identifying a potential property for a given strategy will need to be investigated carefully.
When moving in the speculation mode, understand what the proceedure is in your area for special use permits and who you may need to obtain permission from or better said, who may object, because there will be objections.
Also, changing the use of a property will most likely kill any grandfathered protections from current code compliance, which can be very expensive to comply with in an older building.
Next, I'd check the existing utility services. Actually, in some areas, you may have limited utility capacity for a commercial undertaking.
What lines of cummincations will be required for a project. Are roads sufficient, traffic loads, ingress/egress, traffic counts. When you get into smaller towns and rural areas, you might find that the infrustructure is not adequate. a motel might require a sewage treatment facility, better know that before you buy the property!
I'll stop.....just tons of things to investigate, good luck Charles.
When you get to a specific property, it's all about due diligence.