Avalon casita

I’m building a small 24x16 384 square foot casita with a bedroom, bathroom, and kitchenette. Need to submit to the city for final approval and I need structural engineering as well. The plans will be for an “art studio” so I’ll need plans for just a building then separate plans with details for the space inside. The city will charge too much if it’s a livable space so we will be doing something simple for approval then adding after the fact.