Our boarders insist on storing anything and everything around the electric water heater and its safety is a troubling thing to my wife and I. What is the safe distance away for placing a matress, clothing and such for the water heater?

There really isn't much concern about storing items near an electric water heater, as there are no flames and the heating elements are fully contained within the tank. However, they should take care to not put things up against the hot water pipes (which may be hot enough to discolor or even deform plastic), or the thermostat (otherwise it may be bumped and accidentally changed), and to leave clearance around the drain valve so that maintenance can be performed.

ebaines is correct. However, if it concerns you, make a point of first telling them and then sending a letter outlining what cannot be stored next to the heater.