We live in a duplex with another person living over us. My question concerns animals and renting.?

if the lease says one (small) dog or one cat/kitten allowed, then those are the rules ... the building where i live has the same rules and if anyone tries to move in with a large dog they are told immediately to get rid of it and fined 100 dollars a day until it is gone ... but you might be jumping the gun a bit here ... there is no indication that big dog is moving in and regardless of the lease, at least where i live, big dogs are allowed to visit, just not live here ... i would wait to see what the landlords opinion is and if not to your liking, contact your local tenancy branch and find out what you recourse you have because it is clearly in the lease ... i had a pit bull move in next to me, my patio connected by a four foot fence, and i had that dog gone in mere days ... who wants to live in fear in their own home ...