The quality of the tenant base, historic appreciation, job growth, etc is just too good to be worried about grumblings of rent control. 

If I were you, I would replace any fabric, ie. carpet, I would pay a cleaning company a couple hundred buck to do a deep clean, change any HVAC filters, then I would go to Home Depot and buy an odor bomb or two.

This behavior is in violation of the lease agreement which you signed on (date of lease) which states in section 12: “Disorderly Conduct—Tenant agrees not to permit or suffer any disorderly conduct, noise, vibration, odors, or other nuisance whatsoever about the property and further shall not annoy, disturb, or harass neighbors or other residents of the community and to use no machinery or other apparatus which would damage the property or disturb neighbors or other residents in the community.”

If you're not going to allow pets, insist the building be pet-free and since there are multiple pets in it now, insist that it be delivered clean of all pet odors/materials. 

there was cat pee and human odor throughout the house, the front door had been smashed in and it was without a security screen, the kitchen bench tiles were breaking off and the wood underneath was sinking in due to it constantly being wet and moulded out, the skirting boards were disgusting and the shower had so much soap scum that it took me 8 times with bleach and hard scrubbing to get it halfway decent followed by another 6 times to get it to where it was clean enough.

RE:The house I moved intoI had been in this house several times before, and never smelled any cigarette odors, no smoke odors.

However, a commercial agent did grumble about one once, because I wrote mine as a multi-part offer (which allowed the seller select the set of terms that made the most sense to him/her).

Seller signed the HUD on Tuesday morning and funds were dispersed Tuesday afternoon, so we are officially closed.For reference, this was a FNMA property, and I haven't heard too much grumbling (yet?)

We checked inside the property to find it in deplorable condition - it was drenched in fleas, had an atrocious odor of cat urine, cat feces, and so on.

A bad odor can come from anything, I've been inside houses that have had a bad odor and no pets lived there.