You'll fare much better with a shop vac.Word to the wise... keep the filtration system clean... better performance, less re-circulation of particulates and the equipment will last longer.

Even if there are no parents and children, there are often nieces, nephews, aunt and uncles, cousins and other further distant relatives, whether by blood or marriage. 

If you can afford to, run the newspaper ads daily in the paper up there with the widest and largest circulation; at a minimum run the ads on the weekends.

Fans will only circulate hot, humid air into a cooler, drier crawlspace, creating condensation and causing pipes and ductwork to sweat - you're simply adding more moisture!

Borrowers are eligible for maximum FHA loan financing for non-occupying borrower situations for FHA loan applicants who are related by blood, marriage, or law.

Would it be worth it to install a second floor return duct or trim the doors to create more air circulation because there are none on the second floor.

There's an old saying about getting blood from a turnip...If you can't get above market rents why would you put all of your eggs in the one basket?

I can play devils advocate for LA to juice up your investment blood.

Also the design of you apts is why you have some much circulation space and wasted sf.

(sarcasm) :)We have 5 (FIVE)...........yes five.The key difference is NOT the cats but the owners who take care of them.Many owners do not properly care for their animals.Our cats have always been indoor cats. 2 were strays but were kittens when found.All our cats are domesticated an dhave been tested and cleared.They are spayed and neutered.They never go outside except for our porch on the balcony upstairs for a few minutes then they want to go back in.Having animals is expensive to take care of properly.You have to make sure they have regular vet visits to keep them healthy.Every 3 weeks we clip their nails,clean their ears,and comb them.We brush their teeth a few times a week and bath them occasionally.The only reason a cat will go outside of the litter box is if:1.they cannot access it2.The owners don't clean it enough (how would you like standing in crap to go to the bathroom).3.The owners have too few litter boxes for the number of cats4.The owners let sick cats or outside cats mingle with their inside ones which can lead to many diseases including feline leukemia.I would say in fairness to landlords as pet owners who own our house we are probably in the top 30% of pet owners as far as caring for them.The cats if you clip them every 3 weeks will not do damage to the carpets as the claws will not be sharp enough.Also if you have scratch pads they can that will help immensely.Pets cared for properly have shown to reduce stress,prevent strokes,and lower blood pressure for better heart health.As a landlord you would have to consider many pet owners would fall into the negligence category sadly.For this you have to take on bigger deposits to mitigate the risk.