I understand that water builds up in the rear axle and this causes corrosion in the gears. Is there any way to better prevent this, I ask this because my car will be sitting for four years while I am away at college and will not be able to get around to do regular real axle oil changes so I'm wondering if theres something I could do to prevent this water and corrosion issue.

 

About the only way for water to get inside is either the diff vent is broken or it's from condensation. Not much you can do to prevent it.

Keep it in a climate controlled storage area (heated garage)
Fill the diff right full of oil. The less air, the less condensation
Pack the gears in grease

The amount of surface rust you'll get from condensation, if any, even after 4 years will be very minimal.