On camera, they seem like the perfect young couple and in reality, they are ripping people off. 

Can you do exterior cameras?  

Let's assume they are for argument's sake.You need a sewer line cleaning, followed by a sewer camera inspection, followed by estimate for remediation (if necessary).

I would also suggest getting a camera down in that septic line to see if there are any problems with the leach field and/or pipe (ground may have shifted, possibly resulting in a broken line, or if there are any roots impeding drainage)

They are happy with their iPhone photos or some crappy images from a friend with a point and shoot camera.

I f I was you I would defiantly put fence with cameras ( it will prevent truck to drive very close to houses and damage landscape, + higher price for security).

I have two applicants (they are friends) who want to move in with a nanny for one of the applicant's child.

Will get Outdoor cameras & remote thermostats.

Hire someone to run a camera down the sewer line to the main line in the street (I only have commercial properties and 2 years ago I bought a new $125K sewer line.

Many General Inspectors will do camera sewer inspections.