Better get some help.
Used to reside in a trailer park. I* know, supposed to say Mobile Home Community, but there were more trailers there than mobile homes when we moved in.
Had a tin 8' by 10' shed. Not big enough. Added another. Still not enough. Plus, I was starting to get into woodworking and needed shop room.
Built a 12' by 20'(replacing existing structure so $5 permit) wood frame, T1-11 siding and metal roofed.
Had been building houses for Habitat for a couple years, so framing was pretty easy.
Put the entire building up in three days. Foundation(8" by 8" timbers on 1" pavers), floor joists, decking, and walls framed in one day. Siding, roof rafters, and built/installed the doors on day 2. Installed the roofing panels, ridge cap, and painted the siding on day 3.
Neighbors could not believe I built in in that short a time. It stood for almost 25 years before some one disassembled it(all screwed together) and moved it.