Have you looked at barnpros.com They have pics, tack rooms,lofts,wash rooms..ect. All with prices. They also send you all the things you need to build the barn, you just have to build it your self or hire someone. I think im going to go with them when I can get my own barn.
Depends where you are. A 4 stall barn with the basics is $20,000. It goes up from there depending on what you use to make the foundation, walls, roof. What you use to build the inside, the stalls what type of waterers etc will also affect the cost.
I'm from BC, and the going rate around here seems to be about 20$/square foot or more. That would get you a quality, solid wood and concrete barn, but with no bells or whistles. Just functional and practical. Its expensive! I would imagine pre-manufactured buildings would be cheaper...
Mine was 40K when it was all said and done. I got 6 stalls w/ 2 open spaces that will someday be hay/sawdust storage and a side that will be a tack room. I also got 2 of my stalls that open into the paddocks w/ 2 dutch doors and then an overhang across the one side... with sliding doors on each end... and I got it tall enough for hay storage upstairs (I have to put the floor in)...