How to prove : People not on Lease living with tenant

[Justin Case]

A section 8 tenant has two family members living in the house for the past 1.5 months that are not on the lease. During the day whenever I go by their car is there and I can hear the extra child in the house. How can I prove they been staying/living there?

In my lease it states individuals not on the lease cant stay for more than 14 days in 6 months or they will have to pay additional rent.

The utility bill has been triple the normal charge per month. I have billed the tenant for the overages. they are using more W/S/G than three of my units combined.

The lease is up end of next month. When I bill her for the two other occupants how can I prove they been living there besides saying when I drive by they and their car are there?

Also, I noticed today they are smoking in the unit. I saw it coming out the window. I knocked on the door and it was the extra occupant smoking. The tenant apologized and I threatened to end the lease next time i see or smell smoke.

How can I bill for smoking damage when they move out? Is it just by the cleaning bill from washing the walls with tsp when they move out?

Thanks!