If they are found in violation of rules like authorized pets, authorized guests, drugs, damage to the property, they could lose their vouchers.

Asked if he (assuming it's a "he") could bring a cat (no pet noted in the reservation itself), I replied no, and he replied no problem.

I bring my printed lease and printed addendum / pet contracts as applicable with backup copies. 

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

You're talking about a pet project essentially that could cost you everything you own if everything goes wrong.

What are the pros and cons of pet fees and pet deposits?

I know these landlords have a good business... but renting to students is not for everyone... so know what you want.Demand for rentals in WC is pretty strong... especially if you will allow bigger pets (medium+ dogs)If you are curious or interested in this market, feel free to PM me. 

I haven't typically allowed pets, but I want to know what are standard fees to charge for pets.

There were hairs in the bathtub that I could argue that were his and the cat hair I'd have a good argument that was from his pet as well.   

For example; a $150-$250 "pet fee" that is paid upfront (per pet) and then a $25 per month (per pet) monthly fee.