F.B.
If its a highschooler, I would say $150. ($20 a day plus a bit more).
if it is an adult/ professional dog walker, it might be their daily rate and then some, I think dogwalkers charge $35 a day, so I would round it up to $50 a day.
If its a neighbor, I would pay with a bottle of wine, and a $50-100 gift card to their favorite restaurant/ donation to a charity.
good luck to you and yours,
F. B.