They will test the drain flow, or try to anyway, but a plumber has the actual camera.  

Remember – We have cameras.

Does camera works well even at night?  

Yes, I installed security cameras into rental property so that I can see the house easily without driving there from long distance. 

Also putting up surveillance cameras and signs to avoid any further issues and deter anything else from possibly starting.

I will install remote security, including front and back entry cameras.

I have been guilty of staying cheap in areas that were cheap...never buy properties in bad area is the best lesson...I had  camera installed and saw thief cut the main power line and steal the cameras in Joliet and police reports and police is waste of time and insurance can be expensive...I have had simplisafe wireless alarm system that is great for identifying who comes in and leaves..because you can assign codes to each worker.if you could have a combo system of simplisafe  or another wireless system with a camera system combo that captures who is going in and out might be your best option...you need alarm system with video capture because we still have people leaving garbage in parking lot that alarms can't prevent...I have not come across anything better that has active alarm system with videos.

This way there are extra funds in case of delays or needed architects plans or city mandated extra work like Wired smoke detectors or running a camera through the drain to the street that was not in the budget or time schedule.

Well, I'll pack my camera and go explore Beale Street if I decide to cut out early. 

This can be anyone with a camera and basic real estate knowledge. before you pay your contractors schedule this person to take pics and shoot video of your property to be sure your contractor has done everything they are requesting funding for.