A couple years back, California redefined "Tobacco Products" to include vaporizers regardless of whether someone is vaping Tobacco, tasty flavors, or marijuana. 

This quote included a new vapor barrier and came out to just under 5 grand.

If you are still fearful, then chat with the tenant and encourage them to use a vaporizer.

Why not give your tenants a notice:All painted surfaces have been painted with a startch base in the paint that will turn purple if any painted area is exposed to any synthetic drug smoke or vapor such as meth or K-2.LOL!

I'd cover it with gravel, and maybe a vapor barrier and then pour a few inches of new slab.

Those funds (and more) will vaporize if you don't have the need for 5 people.  

Yes, in power outages, she would not work, but when they kick on, it pumps it all out in minutes, and I just have a dirt crawlspace with vapor barrier so some water is less risk for me....If you have one of uncertain age, actually I might have a back up ready (not just for power outs) because you have to call the plumber, who may or may not have the one you want and may mark it way up.

When rolling insulation batts between the floor joists of the finished upstairs space and a cold unfinished space, I would expect to see a vapor barrier on the side that is exposed to a crawl space or an unfinished cold basement.

But I have two retail vapor stores and I will accept cash rent payments at my stores where we have drop safes and a regular deposit schedule.

She is also requesting that we waive her balance.