Unfortunately every city and township in the country is different in regards to building permits for backyard storage sheds. I strongly suggest you make an anonymous call to you local building department before you start shopping for a shed so you have an idea on the size you are allowed to get and any other codes you need to know.
Play stupid, tell them you want to build a backyard storage shed in your yard, what do you have to do.
Most cities have size and height restrictions. The size is measured in square feet, width times length equals square feet.
I suggest you get the largest shed allowed in your local community. I have heard my shed is too small thousands of times. Very few cities allow more then one accessory building so unless you want to tear the building down and build another, get the size right the first time.
Other restrictions may concern the placement of the shed in your yard. Most cities will have a distance it must be off of your property lines and how far away from other structures or easements it must be.
If a permit is required your city may ask for a plot plan, building schematic and a picture of the shed. You can use a photo from the brochure the shed seller has and they also should provide you with a building schematic.
You can draw your own plot plan. The building department will want to see your lot size, where your home is located on the lot, the distance the home is from the rear property line and the location of the backyard storage shed. For your home and future shed, just draw squares or rectangles in their approximate location.
Some cities will require a permit and some won't.
I always recommend that permits are applied for if required. If you decide to build a backyard storage shed without a permit and the building department finds out, they can really make your life miserable for quite awhile.
You can't fight city hall.