Start with whatever your son's natural talents and inclinations lean toward.

I'm inclined to take an offer and move on.

. - which I suspect you're already inclined to do.You can also investigate various methods of pipe replacement / renewal that involve trenchless technologies, such as pipe lining, pipe bursting, or directional drilling.

If I see progress soon I'd be more inclined to recommend them.

Send it certified mail, return receipt requested if you are so inclined. 

I “cash flow” about $7,000/month but because I’m not mechanically inclined I source out my maintenance which costs me roughly $4,000 of my cash flow each month.

Without knowing your age, I like the idea of pushing additional savings into good, no load index funds (I like Vanguard's S&P index but there are plenty of others) through a Roth if you're young enough, leave the rental portfolio as is and pay the debt down to nothing, since you're not inclined to really work at growing that end of it. 

Some owners would prefer a clearly defined floor even at the cost of not rising to the highest ceiling.While I hate to say it, there are also property owners who lack either the time, knowledge, inclination, or skill to want to manage their property effectively.

At this point I'm inclined to average fuel usage over the last few years and come up with a heat included number to add to the rent.

With limited experience in RE investing my inclination is towards RE, not stocks.