So I yell out to him—no response.The thud side had no shrubs just concrete, so I though maybe he had just broken an arm or a leg.

If you have need of help or suggestions on anything my background is working for the 219th RED HORSE squadron as a Structures troop for 10 years, in civilian contracting for carpentry and concrete refinishing, as well as property management just to name a few things. 

Perhaps I will check with a real estate attorney tomorrow and get the ball rolling.I've already heard the horror stories of tenants pouring concrete down drains on their way out.

But before actually starting on anything, it sounds like you should do some reading and work on writing with more polish.

Any feedback from anyone on the craftsman 2015 National construction Estimator - there are 10 specialized areas on costs.National Construction Estimator National Home Improvement Estimator National Repair & Remodeling Estimator National Renovation and Insurance Repair Estimator National Electrical Estimator National Plumbing & HVAC Estimator National Painting Cost Estimator National Earthwork & Heavy Construction Estimator National Framing & Finish Carpentry Estimator National Concrete & Masonry EstimatorI am thinking maybe the the second or third ones would be the only ones needed for flipping homes. 

We wanted to use this 500 sqft addition in the back that has no windows and is on a concrete pad as a garage.

We do some (very little) of the work but mostly contract out the big stuff like Kitchens and flooring, our contractors that we keep close are an Electric, Plumbing, Flat work (concrete), and a good foundation guy (basements leak and or crack around here and that work can be very expensive from a big companies).  

Hopefully your crumbling concrete is a small localized area and can be fixed easily.

Promptly bought my own setup.If a field goes bad some municipalities require relocation to new ground, and of course current standards, which could involve, pumps, alarms, aeration chambers etc.I had homes in one city where you weren't allowed to touch an existing field, and when they died, I was forced to hook up to city services @$5600 plus monthly fees.All depends on how your dirt perks and the prevailing "rules" as far as replacement options.I have heard many times 50 to 60 years is all you should expect from a "system" and even concrete tanks can fall apart from the extreme environment they are subject to.    

It might be put off to the concrete company.