I know this varies, of course, but roughly what are the expenses involved in putting in a "bare minimum" type of wash stall in a preexisting barn with a dirt floor? Could be with or without hot water.
This assuming most of the building could be done by those who own the facility...
I would think a big part of that would depend on the distance of pipe and type of drainage system. This also depends on your building codes. I would start with finding out what is required (septic, etc.) Is the water line there already? What kind of water heater?
Ours really was just the cost of the concrete (somewhere in the vicinity of 2 yards), some gravel (probably at least a ton- we already had a pile-for under the concrete and the drain lines), the drain itself ($20)and some perforated pipe. We had re-bar for the concrete and lumber laying around for forms, and we already owned the concrete tools (bullfloat, mags, trowels, edger).
Mine is a private barn, and the wash rack isn't used a lot. We ran the pipe downhill to a dry well. We could have run it to the septic tank, but I don't like to dig up septics any more than absolutely necessary! Haven't had any problems with it. When I'm not using it regularly, I duct tape most of the top grate of the drain to keep hair/dirt/sawdust out.
Around here, the minimum load of concrete is 3 yards. You have to pay for three even if you only need two, so we had something else formed up to use the remaining concrete. If you have nobody with experience to help with concrete, don't attempt it on your own. Besides being a lot of physical work, concrete can be finicky. A few years ago, DH and a friend and I poured a wash rack/tack room slab for another friend. As we were all sitting there on buckets, drinking beer and looking at the concrete, she finally couldn't stand it anymore and said "I know I don't know anything, but what are you all doing?". We just chuckled and told her we were just waiting for the slab to be ready to "work".
Plan! Plan! Plan! where is the water is going to go? Especially in wet weather and cold weather. Do a percolation test. I've seen so many wash racks surrounded by mushy, muddy, mess. Check to see if you need building permits so you don't get a fine, or Stop Work order.
I know a friend just wanted to do the drain field since it is just her private barn and her county required a septic. Which was a big bummer for her, and suprised me because she is zoned agricultural and not really a "city" farm (as those seem to have much more rules to follow). So do check your regulations.
Just make sure you have adequate drainage and the concrete is sloped correctly towards the drain. My wash stall can only handle one horse every couple of hours. I didn't build it, it came with the barn.
I have stall mats in the wash stall, cut a piece out for the drain, which helps with drainage. I replace the plug when I'm not using it for washing.