Renting with priceline or other like companies?

[j3nnifer]

Hi quick question! I'm looking at priceline and cannot find any information on this!

If i rent a car from priceline, i see i will be charged for the total amount of the rental, now when do i pay for the deposit? Is it when i get to the rental car place? Will i have to use the same credit card? and can you use your AARP card to get the free additional driver( i'm planning to rent from hertz)

hopefully someone can answer this for me? .. I'm leaving out on saturday Thanks!!