If your goal is to grow your LLC, consider arranging all of your properties under an agreement with your LLC to manage them & take all of the legal steps to ensure that the structure is correct. this may involve creating LLCs in the state(s) your LTRs are in to own the property and your PM LLC managing those properties, so that you don't have a concentration of all of your portfolio in one entity.

What is likely to happen is you try to solve HER problem - just to have it repeat.You really cannot evict one person w/o evicting ALL OCCUPANTS.Know you think you are doing the right thing, but you are NOT.The only way you can/should assist the mother is if she files a police report on the other occupant.If mother is not willing to do this, do NOT get involved!

I cannot find anything specific to dryer vent cleaning anywhere.

I grew my rental portfolio starting with a house hack to rentals that are all clean BRRRRs.

And don’t pay anyone or sign anything before you get your carrier involved.

If you can get in with a real estate brokerage that is more involved with investors you will learn a lot more.

Some land was sold off years ago without this issue, but I understand why the attorney can't guarantee clean title.Has anyone dealt with something like this?

Keep in mind though that finding partners takes A LOT of time as you want to actually build a relationship with said partner before getting any money involved.  

They also have very rigorous requirements (again test results near or just below the detection levels) for getting a "clean" house.

I also have a close relationship with the cleaning company, so that part is covered.