A tenant cannot be charged for ordinary wear and tear to a carpet. And from the sound of things, this is the carpet that was in the unit when your father moved in 17 years ago. That having been said, to the extent that a tenant (or their pets) caused additional damage, then they would be liable for the cost of a replacement carpet. Again however, after all of these years it will be hard for the landlord to make such a claim and charge you.