I agree with rentalguy. $50-70 /day seems to be about average for a minivan off peak. At the beginning of the summer Enterprise gave me a one-day weekend rental of a minivan for $45/day. I have a reservation with Avis for a minivan for the middle of the week towards the end of August for $53/day. If you wait, the prices jump up, or you won't be able to get one at any price. The few exceptions may be Hotwire at a small airport for $130/day or Rent a Wreck for $150/day.