The simplest and least expensive way I have seen to store bikes is vertically, with the front wheel hung on a J hook screwed into a horizontal 2x4 or 2x8 (whatever you have) attached to the wall. The height of the J hook should be high enough so the rear wheel is on or just off the floor. The bike can be rolled in an upright orientation to the area, lifted slightly and hooked in the upright position. You can alternate hanging each bike by the front and then the rear wheel, for closer positioning of the J hooks. Or you can space the hooks farther apart and hang the bikes at an angle to the wall instead of at 90 degrees to the wall, depending on the dimensions of the shed.

If a person (small human) is strong enough to stand a bike on end and roll it, and if he/she likes the bike enough to roll it into the shed and take care of it, that person might be worthy of another bike when the present one is outgrown. My philosophy is that a bike that is allowed to rust is looking for a new owner. It's probably a good thing that I have no children.