My bitty coops and pig sheds got WAY cheaper when I realized they're not load bearing. You do not have to build that to code, and OSB is fairly self supporting. So now I use at least 80% less framing than the first one I built. Muuuuch cheaper
Also, paint is a preservative. I painted OSB - which, lets admit, is cheap crud - with that thick, oily barn paint that takes 2 days to dry, slapped it together with just enough framing to nail to and built a mini-shed that housed a sow and her litters for 6 years before it came apart. And pigs are rough on housing, that little thing stood up to a LOT of piggie butt scritching. It actually didn't give up the ghost until a horse decided to get in on the butt rubbing.
Another one that I bothered to repaint once in a while I had for 5 years, then gave to a friend who needed a tiny shed for ducks, and she still had it 4 years later, and might have it yet, I haven't been to her place for quite a while.