They excavate the sewer main for their tie in, while exposed they cut my active line and capped it. 

The plumber will likely have to cut open the ceiling to confirm and make repairs, so you can save a little money by learning how to do that yourself, confirm the problem, and then call the plumber for repair, then patch the ceiling yourself.As Jonathan is trying to point out, it's important to expect these things and have funds on hand to deal with them.

We had nine months straight of increasing inventory.

They do all the work and then they take a cut.

We found out the potentially the whole block has led pipes so we are needing a contractor to cut a hole in the floor.   

Lawn cutting/snow removal you can get quotes for, plan for some vacancy, property management software if you will use any.Hope this helps.

Prior to losing the home in foreclosure the previous owner had retaliated against the lender by cutting out most of the exposed electrical wiring and removing the heat and air units from the property. 

Document all of what you do if you are going to get it done for them, and/or if you cut them a check then make sure it is in writing that it was all done and they cannot come back to you at a later date asking for more money/mitigation.  

It is usually fairly cut and dried.

Most spend too much of their time and resources on the set up and completely ignore the day to day responsibilities and/or cut corners and costs where greater attention and resources should be spent.