Price
Each lbs cost $10,000
25,000 x 10,000=
$250,000,000 for one year worth of supplies
Problems that may occur: Running out of water (Once reaching mars each person will get 3L a day while saving 12L extra each day)
Water weighting too much (Going there we will need to carry 25,000 lbs of water for minimum survival)
Water Contamination
Water for plants( once they get there they will have 12l extra of water a day but some will need to be saved for emergencies)
In my option we are not ready to send people too mars. It will be too much money to keep sending supplies but if they figure out how to get more water once they get to mars their chances for survival is greater.