So my zero debt rental properties fall in the core and provide the stable foundation to do other things with the rest of my portfolio.Also, it was possible to buy decent properties in my area of the country (Tampa) in the $100K range five years ago or earlier, but not anymore as prices have gone up too much.

I like that approach.It's conservative and gets you the solid financial foundation you need.

In my area poured concrete foundations are the norm , cinder block is mainly done on additions and small jobs .  

I know both areas, can develop relationships with key team members in both, and can tell if a property is a good deal more easily.This isn’t the rule for all investors, but makes for a more solid foundation from which to begin.

Can I defer foundation maintenance?

The outside of the house looks well maintained and cared for, not in obvious distress. perhaps there are foundation issues, but it's block and beam so I'm not entirely sure how difficult that is to fix. it has window units but lists as having central air, possibly it's broken?

I don't usually do that but there was a flood that caved in a garage foundation wall during the due diligence period so definitely made sense under the circumstances. 

The inspection report said that the foundation is fine and that the cracks need to be sealed and painted.

There are buyers out there who do not mind foundation work.

If your personal financial foundation is solid then learning is easy because you can find realistic paths that will fit where you are.