I do know managing more than 1 property is a tall task unless that is pretty much your job. 

If we stay with our high-paying jobs, we can carry the properties, but we(spouse and I) are too afraid to invest in Class B or C neighborhoods.

I'm doing quite a bit myself but the cast iron part is a job bigger than I can handle.Any recommendaitons for rough-in plumbers in NJ and willing to travel about 15 miles outside of Newark?

Eventually, I’d like to start using the cash flow to pay myself and work toward replacing my day job income.

GC never pulled any city permits yet charged me (didn't find this out until the job was finished). 

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.

Other risks, the contractor walking off the job, a storm hitting and delaying the project for weeks, someone breaking into the home and stealing stuff (which happened just the other day to a client of mine), a squatter, or drunk driver driving into the house (happened a lot at my old job as a firefighter lol).

My job is explaining the rules.

You don't need to save up $100K or quit your job today in order to become a successful investor. 

Also, what niche jobs in real estate (Agents, appraisers, house inspectors, lendors, ect.) are going to be replaced eventually?