Fifth Wheel Garage

I am getting my funds together to build a 30x40ft metal building on a slab. I want to be able to store my bass boat and a 30ft fifth wheel in there. How high does the door need to be, 14ft? Has anyone built something similar and would know approx. cost to build, concrete,metal,ect. I know it varies from one part of the country to another. What do you guys think,20k 30k 40k ? Any answers would help greatly in my planning.