I’ve gutted the house and painted two coats of kilz, the house still smells really bad.

If it only needs a coat of paint, you can't hardly screw that up.

Colored OB PEX should have a gloss coating to it which is the barrier. 

Even if tenants pay base plus cam to landlord they generally do not have the funds to cover parking lot or roof right away and landlord has to pay upfront and collect cam over the years to make it up.If you want to fully update the center for new roof,re-coat and stripe parking lot, new paint and facade etc. it could run into the 6 figures for that or more depending on building size.There are companies that buy shares but they want a discount. 

Also some of the older homes could still have soap/dirt/grease coated drum traps that invariably freeze & are tough to get to. 

A truck bed coating like "Raptor Liner" would likely also deaden the noise transfer.

Just recoat the hardwoods with another coat of poly every couple years to make them look better.  

Do you just go with bland neutral colors (eg a coat of primer and grey/tope) or do you do something else?

Thanks @Monique Rene Coates, that totally makes sense! 

That's a tough start, not gonna sugar coat it.