Congrats! How exciting! The following got lengthy, and may be way more than you wanted, so please ignore as needed.
Our place wasn't from scratch but was/is a major redo.
I echo that weather and climate is huge. We are in NC, so take that into account with my story. I am thrilled with my shedrow situation, and the horses love it. I can't imagine having to catch and lead horses in and out after having our situation...so much easier. I have two horse who get along great...I think personalities and dynamics may come into play with plans as well, so another grain of salt. The Little Red Barn (shedrow with overhang) was set up with three small stalls when we bought it, with one side closed up from the edge of the "porch" all the way back. Also had a piece of the adjacent front closed in...looks like an after-the-fact aspect and is probably due to weather/wind/rain. Long story, barn was not horse friendly, needed major shoring up just to start redo, but it had good bones.
So, if you can picture this.... we borrowed 2' from the porch to make stalls 12' deep. We made a 24' wide long stall with 2 doors with thoughts of later putting in a wall to cut it in two if we got a third horse. We made the second stall perpendicular to that space, using that enclosed area I mentioned. That second stall ended up being about 20' deep and 11' wide. So the stall area is an L if that makes sense. The horse love the huge stalls, and I am able to use that 12x24' space with 2 doors as a come and go as you please refuge from wind/heat/sun/flies...horses get along great with very clear leader/subordinate, so we haven't had any safety issues. We keep door to second stall area closed at all times, as it only has that one way in and out. DH also built on a 26' long area, as deep at the barn (about 20'), as a continuation of the barn for additional shelter. I feed hay there. It's open on 2 sides, barn on 1 side, and fenceline as back side. Barn ceilings are very high. Lots of air. Horse and vets love it. Stall gates are handmade, and DH read about 4' width for stall doorway, decided to go bigger for my very big boy, then added a buffer, so I think they may be 5' wide. lots of clearance for hip bones.
The fenceline comes off of either side of the barn and creates a 1 acre "barnyard". I have 2 additional pastures, about 1 acre each, on either side of barnyard. Sort of forms a U. At night they stay in barn yard, during day they have access to one of the two other fields, allowing for rotation. For the most part, no halters needed to turn out or bring in...they know the routine and they also, mostly, come when called. Water trough in each pasture, though they tend to prefer the one in barnyard or the buckets in that double stall.
We have just shy of 12.5 acres, 3 of which were hayfield when we bought the place, and we continue to hay those...they are unfenced. Originally I planned to fence EVERYTHING but after doing enough fencing yourself and paying for enough materials, plans can change.
And having hay fields has been very nice, since we have a neighbor to hay them.
The way this place was set up, the house is about 1/3 of the way back, dead center, in a perfect rectangle. Huge front yard (a waste from horse perspective but DH loves it so it's fine by me), hay fields on right and left of front yard. Big back yard for dogs. Barns are at about the two thirds mark of property, behind house and back yard. Pond and some land at very back, woods on either side. I love this lay out as the horses are sort of hidden at all times. It makes me feel safer. And they have a buffer/distance from whatever neighbors are up to. We also have the fencelines set up that you can ride (and mow!) between our fenceline and the neighbors' fences (which are on property line...cattle, so barbed wire) as well as between outer horse fence and back yard fence, along with thenon-pasture areas of property). Sort of a perimeter track.
I love that there are two barns. Second barn is outside barnyard, but very close. Used for hay and other storage as we continue to work on horse barn. I like having hay separate for several reasons. At the backside of shedrow horse barn, there was more storage, and we turned that into a future wash pit once we have water hooked up, and what will be a tackroom/feedroom.
We ran water and power. At this point there is a yard hydrant outside fence down by barns. I don't even have to run hoses to stalls...so close I just carry a bucket or two. Use hose for troughs in barnyard in two pastures. Attach hose to house for third pasture. (We are on a well).
Random things...we did a bit of driveway work and created a jughandle that makes life easy for the UPS man, as well as trailer turnaround. Also widened a bit for trailer parking. Avoided a separate parking area for trailer by adding width, so cheaper. Also used crushed concrete in place of gravel....half the price! We have lots of gates. 12' wide. Have gotten all sorts of vehicles and equipment through them, including dump trucks. More gates than we typically need, but on that occasion when you need it, you are thankful! There is 1 place I wish I added a small gate and it still bugs the crap out of me every time I have to walk around to use another one.
We will be expanding the L of the horse barn to make a 12x12 for a donkey or two. Roof will be lower than other stalls due to pitch, but will be fine for donks or a small pony. Wish I had realized pre-run-in addition that the huge stall would never be converted, as we would have just gone longer and added more stall space, but it's not a problem unless we sell the place and person dislikes that lower ceiling height in that one stall.
Poop...have a pile in the woods. Has its own gate, lol. I drag the pasture with a four wheeler and a drag. The pile is from stall time...meals, bad weather, hang out time so less waste than if horses were in half the day. So far out hay guy has hauled off for us once in the not quite 1.5 years the horses have been here. Did have the pay. We thought we'd spread on hay fields but apparently that doesn't work as well with cutting square bales vs round bales and you cut grass shorter and poop can get in square bales.
Make sure your plumber and electrician are familiar with barn work. They actually helped me come up with the best way to do things after I told them my thoughts...they had an idea or two to improve my plan. And they were up on code requirements and materials needed and suggestions to help with freezing (plumbing). Plumber recommended extra shut off valves along the way, so we have one in pump room at house, one at yard hydrant, and one when we hook up water in the as yet unformed tack room. I got good advice from the DDBB group as well re: switches and such for the power....when it comes time for that for you.
The original owner did a pretty good job thinking about things like run off and wind. Not perfect, but really pretty good. We have struggled a bit fixing some water issues, so I would really stress paying close attention to what your land says about wind and rains at different times of year. And it may help to have your county extension agent out...sometimes they see things we miss, using fresh eyes that have seen lots of farms and really know the area.
Have a wonderful time!