18 yr old dying dog - rent to them?

[Andrew S.]

I'm advertising a 1 bedroom house (450 sq ft - half sheet vinyl / half carpet). Current best prospective tenant has an 18 yr old chihuahua that is dying of cancer. Renter is a seemingly mature 50 year old woman with a 16 year old son, dad works away 2 weeks on/ off. The dog uses the bathroom indoors on those pads.  

Is it likely that the carpet will not get ruined? Can't decide if I want to rent to them. They're fine paying an extra deposit and extra pet fee. I generally don't allow pets.