Fresh paint in a light neutral color and the place being super clean & not having an Odor (maybe put in air fresheners) & taking nice bright clean photos for the rental listing is the biggest bang for your buck in my opinion.

That's not really a good idea for moisture, but okay for odors.  

We tried: 3 different types of enzyme cleaners that had good reviews, water and vinegar, soap, essential oils, lots of scrubbing, cleaned our air ducts, and most recently an odor sealer on the floor that dries clear.

I recommend the latter, though the fluidity of offensive odors often complications removal to the point of fiscal irresponsibility.

Cat odor is difficult to get rid of.

Smells can make a difference -is there smoke, mold, odor of pets? 

Anyone have any tips on illuminating/reducing odors?

Hoping to get them all installed next week.Plus odor removal (smoking in 2 units with acoustical ceilings removed and that will be replaced, plus kilz everywhere on the floors and walls, and what smells like a dead dog, with urine and feces in another apartment), completed carpet removal and am starting painting and need new appliances.Oh, and some electrical things are on movable plywood panels, that will need to be dealt with.Pretty total rehab. 

Foul up in their system since they normally only did year leases. 

Get a quote to have the odor neutralized and with hold that amount from the deposit.