I work from home and was in need of more space for my art projects. I started out researching many prefab structures from Modern Shed, Modern Cabana, Studio-Shed, Kangaroom Systems, etc. Initial estimates from these manufacturers looked good initially. However, calculating total cost after adding concrete slab foundation, plumbing, half bath, and and electrical sub panel would have brought a prefab the cost closer to what I would spend having it custom built.  Amazing Modern Backyard Office by Aaron Britt