My best cheap cage is a Midwest Wabbitat, 37"x24"x19". They ran me $40 to $50 each and work well for one adult rabbit. I have room for a large attached water bowl, a feed bowl, crate mats, and we give them a pine hide. They can hop up on it or go under it. A mat fits perfectly in there. I first started using them for quail and now I have 10 for rabbits. The bottom trays are fairly robust so far, and are easy to pull out and dump to clean. I can stack two fine. They're easy to set up and also take down to store. Although I doubt I will be storing any in the future!
I bit the bullet and bought KW model 4000 cages, 30x36x18. I have enough for two 3 stacks. I use them for moms with litters and grow outs. When I went to the Klubertanz website and added up all the parts to make three cages, it was almost the same as buying them pre-made from KW with the added heavyweight floors. That was before the cost of shipping everything.
That includes legs, urine guards all the way around, extra heavy floor, support beam across the middle, deep metal litter tray and the sliders for that. If I had a barn I would certainly have gone with making my own and hanging the cages at some point. Not having to clean litter trays would be a huge plus!
We are zoned as suburban half acre though I have 2/3, but the flavor is semi rural because of the lot sizes. Still I don't really have any place to put a small barn. I have a small aviary based on a really nice dog run that we sided and roofed, and a well built and sited shed, a couple of wood piles and a large second garden, plus oaks and apple trees. I don't want a shed in middle of the view from my back patio! And a shed would get too hot. The sides of my run are heavy duty welded wire from a dog run, plus we have light bamboo roll screens for shade, and a solid sloped roof. They need the air flow. It was originally a dog run attached to the side of my garage so we could go out the man door to let the dog out at night. We have mountain lions, bears, foxes, raccoons, owls and hawks. We heard too many stories about mountain lions getting dogs. Once we built our fenced patio with additional snake fence, we didn't worry as much because we were always outside with any dog that was outside. So the dog run became a greenhouse. Then became a second aviary. Now it's a rabbitry. As it is if we also put cages on the concrete floor under the benches that we built, we can stack 3 for 15 cages total.
We can get away with this 6 ft x 16ft run attached to the side of the house and roofed, and I can make it 6 ft longer, but I'd like it to look less tacky, lol. But not much space to really expand.