The upstairs unit has a very strong sulfur odor from each tap regardless of it being hot or cold water.

I shall grumble grumble grumble at the closing and sign and pay anyway.Thanks for the advice. : )

Years ago I investigated a gas explosion, a new bank building called because of a gas odor, the bank was evacuated except for a gas company employee and the bank manager and a leak confirmed.

The house I showed had issues since the prior tenant had 2 large dogs and I had lots of scratch marks and a bad pet odor. 

The distinct odor of marijuana smoke was wafting from their apartment into the parking lot.  

Short of demo to the studs, is there any cost effective ways to eliminate the odor?

Spray them thoroughly with Awesome Orange cleaner/degreaser (this is an amazing, low-odor cleaner you can buy at Dollar Tree).

Traffic, parking, noise and odors.

HD also sells these odor eliminating rocks that come in a little pouch.

These areas must be respected and maintained in a clean, orderly fashion - included but not limited to trash, debris, odor, unattended possessions, music or noise etc - by penalty of $100 fee per incident.