How simple and inexpensive?? Mine have had as simple as stringing a tarp across two round bales (sorry can't seem to find my pics of that one).
You can use cattle or hog panels as a barn/stall walls/roof and run a tarp over the top. I've just started a chicken "hoop coop" - it's not finished yet. The long sides are 10' and the short sides are 8' (2x6's - so a little shorter than those lengths in actuality). This one is made with 2 cattle panels (50" x 16" and just $20 at Tractor Supply Company) - making the long side about 100". It's tall enough for me at 5'6" to walk standing up in. We plan on also doing temporary hoop coops to store some equipment for now - later we will build a 3 sided shelter with the front opening able to be tarped shut in bad weather to replace the "hoop coop" storage units.
Before winter, we will have a back on this out of plywood and a door on the front of it. Will probably just have a larger silver tarp over the top - to cover it and fully cover the sides. Otherwise, thinking about the panels that let light thru - but this one is movable and since I used 2x6's it's already unbelievably heavy...
You can do a 3 sided shed w/ walls out of panels or combo of panels and wood and gates on the front. RDU Sheds or
West Wind Shelters .
I've used dog kennels in our carport to foal out our mares as large as 45" in height... The pic was taken from the open gate. Not sure of the size of this one... I actually have 3 pens here - this "stall" is the largest and on the outside. The tarp showing in part of the photo was put up on the kennel side that Koalah is facing for a storm that hit later that week... and also again the following winter allowing us to foal out 2 mares in between snow storms here in NC.
This photo shows the "stall" after the larger one has been removed (used somewhere else) and another separating panel between the two front gates has been removed as well to make one stall still under our carport that is now 10x10. Pic taken of Bit after she aborted her colt and was very sick for a while - from our kitchen door.
and here is a stall made out of some gates I'd brought to NC and wasn't using yet on the leased property. The solid boards were OSB that had also come down from MT w/ us. This is under a tin roof attached to a tobacco barn that we were using for feed and tack storage.
THis one is huge - sorry!!
This shows Magic and Pixie in the back of the "stall". I used 4 - 8' gates (that aren't quite 8' wide). That makes the stall 8x16' long... The boards are just tied up to the gates with haystring thru holes that I drilled in them. It worked as a temporary stall for many uses for 5 out of 7 years before the OSB "died" from the wet weather and the gates were used on paddocks that we put up. Those same gates have now been used on several different paddocks and pastures at our new place here in Lillington. Two of them will need to be replaced soon - the bottom rails are rusting out and they are 20 years old now.
If you google Pallet buildings, you can see many things built with pallets both on websites and on YouTube. Here is the one I'd like to build -
Pallet Shed . I can get 48x48" pallets w/i 20 miles of me for $2 each. Not free, but pretty darn close! I think you could do something similar for a barn for minis...
When you decide what and how you are going to build your barn/shed/stalls - let us know! Pics of what you do/have built would be wonderful!