My updated expected monthly rental income will be $2,800, resulting in a cash flow of $795 per month (excluding my share of the split utilities).I plan to set aside at least 80% of my cash flow for property-related expenses.Additionally, I’ll be installing keypads and security cameras for enhanced safety and operational efficiency.

Interesting idea, but I suspect that would create more problems than it is worth.Most of the leverage you have with a NNN lease is that you are working with a company, presumably one that makes money. 

I’m thinking” not my problem”- you are the builder.

Some others have had communication problems, but I've always been able to get a same-day response. 

No problem, work from home that day etc....

What are the biggest challenges people have faced with this. Also how do I make sure to get good tenants?

No problem at all. 

That way the properties don't overlap and it doesn't cause any problems. 

Even the best property management companies (PMC) struggle with:- Finding reliable handyman and contractors (ServiceTechs)- Same with affordable ones- Tracking preventive maintenance- Tracking previous work for potential reoccurrence warranty coverage- Understanding tenant reported problems, so the correct ServiceTech can be dispatched- Determining if tenant is at fault for an issue & should be charged - and will proof stand up in court?

Is there a specific challenge you are trying to solve for?