Ideas for New Shop
Build it as large as you can afford. A 50 amp 220v service should be adequate, unless you plan on adding AC. Hollow core doors make great building boards, for work bench sufaces use good ole plywood sealed with urethane. See if your kitchen counters would be a good height for you, if so go with that height. Do you prefer to sit when you build? If so build them lower. I myself like to stand when I build so a 36" height works well. Don't forget lots of light and leave plenty of space for storage.