How big is your snake? My female ball python can go three weeks, but my male would be angry. Fresh water will also be a major concern over that long a time. Someone is going to have to come once a week to make sure there is water, again the size of snake, the tank set up, the depth of the water bowl will dictate how often someone needs to check up. If it is just one snake can your friend take the snake tank and all to their house?