In my time as a Realtor, I’ve had a few listings that were 100% pet free since new. For some buyers, this is a major plus. Showing a home today, I had a buyer sniff twice and say “cats!”. The issue may not just be a litter box smell, some clients are highly allergic to cats. Similarly, some prospective buyers have issues with dogs and other four-legged creatures.
My advice in dealing with pets in your home sale is to clean and deodorized as much as possible. If the animals can stay with friends or family during the period when your home is being shown, I would take that route. Otherwise, have the showing instructions state something like “four-hour notice required, owner must remove pets from home”.
If you don’t have pets at this time and are considering selling your home, don’t complicate things – acquire that new puppy when you have relocated to your new home (with fenced in backyard).