It will also have more blowing power so could shift the lint that's left in the duct and create a blockage that could start a fire. 

I would tell them they can enjoy this "extra" that most other landlords would exclude BUT as soon as there is a disposer jam, a kitchen sink backup or blockage...I am getting rid of it. 

(Think 2-3 months prior Covid 19 moratoriums attempted to block eviction but unsuccessful before lockdown blockage).I kept “joking” what if the tenant I can’t kick out was using drugs what would happen?

But, that doesn't mean I had the correct mindset for investing & managing my own stuff, a bit of mental blockage there.

While these products may be marketed as a convenience item in this way, the truth is that these types of items have the ability to clog and stop up not only the sewer line on this property, but also can cause blockage and service problems in the public sewer system and pump stations.Unlike toilet paper, these products DO NOT break down once they are flushed.

My preferred plumber would've charged $350 to jet the line.Upon arriving 10-15 minutes after the job began, I confirmed my initial assessment of the blockage.

By your description of the work needed, it certainly sounds like the pipes are seriously deteriorating (from the inside), or possibly broken, sagging, or even offset if the blockage is outside of the structure en route to a city main or septic.

Had it camera ran down about 300 Showing me where the blockages were happening, and how deep.

Is they're roots cause the blockage ?

Talk to them and ask them to diagnose for free, but if it is a blockage due to other sections of pipe or improper waste in the drain, that is going to be on you.You may also want to call the city and check with them, especially if you had heavy rains before it happened.