We have gone as far as ripping out carpets, then continue spraying every few weeks for a month or more, before installing new carpet, painting, etc.

I'd recommend you spray (instead of brush or roller) for a perfect finish.  

However, if I just let everyone know "someone" has tested positive it will have the same effective, as two of the apartments are friends, and one apartment is currently rented but not occupied (living with a girlfriend out of town for months), so to say someone has tested positive is identifying that tenant, effectively.Common area is only the laundry area, but I don't know if it's practical to go there daily to spray down the entire area. 

So while the "standard" American translates "preservation" as something akin to putting $ in jars and burying em out back, "elite wealth" translates Preservation into a action, growth, consolidation, they are doers. 

Clean mountain air and ocean spray.

If you plan on having internal combustion engines of any sort in the garage below, don't skimp on air sealing the garage ceiling and walls {this is where closed cell spray foam insulation is very useful}.

I'm thinking maybe spraying something under the sink and sending a text to her (so it is in writing).

(spray and pray style?)

Wholesalers will spray the deals out, but if you know repairs and get on the lists you can get some deals.

The upstairs unit is in good shape with a little cleaning, but downstairs a previous tenant clearly had a cat with a tendency to spray in the house.