What can you build without a permit?
There are many cosmetic changes to your home that can be done without a permit. For a fairly extensive list of those, you can click here.
The largest stand-alone structure that can be built on your residential lot without a permit must be detached (at least six feet) from your home and less than 200 square feet, one-story high. It cannot include electrical, plumbing, or heating. If it does include electrical, plumbing, or heating, then it will require a permit.
On your commercial lot, the maximum size is less than 120 square feet but there may be additional steps required from Planning/Zoning.