It is very likely the tenant is growing weed as well which creates a very strong skunk like odor. Look into a device called an an activated carbon filter.
Maybe suggest or purchase one for both neighbors. The filter needs to be replaced every 6 months but should take care of any lingering odor and also filter the air
Costco has some amazing wire shelving units that keep my rigs nice and sturdy! Here's the link to the one I have.
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Also, for fans, I use 6100 rpm 120mm fans by Parallel Miner. If you dont mind your rigs being loud as hell, then these are the fans for you. Just make sure you have a fan hub. I like the Thermaltake fan hub for the fans. Though, if the fans are just pushing hot air back into the cards due to high ambient (room) temperatures, you would want some type of ventilation of cold air into the room. I would suggest a vivosun inline fan with a tube going from outside your house, and a filter in between to trap dust and leaves and such. I hope this helps! Links to everything below.
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VISOSUN INLINE FAN BUNDLE
PARALLEL MINER 6100 RPM FANS
THERMALTAKE FAN HUB