One thing that we do re maintenance is to have all contractors take digital photos before, during and after the job. 

My top business-related apps : Landlordy (rental income/expenses management on iPhone), Mail2Self (quickly email to yourself any web page you have visited and want to follow up later), MileIQ (automatic mileage tracking), Dropbox (obviously), WhatsApp (communication with tenants/vendors), Scanbot (digitizing paper into pdf files), 1Password (keeping my passwords safe and unique), Soulver (smart mix of calculator and Excel-like capabilities).

It takes work to get high double digit returns.

They won't take you from rags to riches overnight but they can produce consistent (high) double digit returns with 10 year, non-recourse, 30 year amortization debt.There are no guarantees and some markets are definitely frothy and there are financing and property strategies to help mitigate the risk.

It may be as simple as replacing the main line out of the tank that goes to the drain field but you wont know until you dig it up, so I would plan for the worse case scenario.  

Also, for future issues like this, can you purchase a camera/dvr system and point it at the drop box?

In the mean time, I would always encourage anyone to look for long term rentals that they can get a good double digit return on as an investment strategy.  

That's not to say that you won't get double-digit returns over the hold period but you just won't get them out the door. 

I'm am comfortable enough with my own abilities to skip home inspections but I will often still pay someone to send a camera down the sewer line.

Mediocre deal at bestYou might as well put all that money into a dividend stock that yields 2.5% and call it a dayjust LOL @ spending large amounts of time and resources to retrieve a single digit return when you can accomplish the same thing with dozens of other kinds of investments with virtually zero time and effort