Re-building Barn/Workshop...Noob Here!
Have you talked to your Planning and Building departments.
They usually have guidelines on what is required for submitting plans. Many time their guidelines are easy enough for a DIY'er to produce the plans for a small accessory structure like this then pull permits. You should find those at the Building Department.
Planning will let you know setbacks form the property lines, building height restrictions (if any) and things like that.
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