Become acquainted with zoning ordinances, deed restrictions and building codes. Depending on your area, you may need a building permit. Building codes may determine how far storage units must set back from property lines and what materials are acceptable for siding.
If you want to go a step further and separate your tools, you'll need to get a bit more creative. One way is to utilize PVC pipe to make containers for your tools by attaching to two pieces of wood and hanging that from the wall. Another solution is to utilize a pegboard for your larger items as well, as they can hang from hooks similarly to smaller items.