We have about 10 boarders and around twenty lesson horses. Any of the lesson horses are up for lease so it depends on who's being leased. Then we have a few horses that aren't quite ready for lessons and are 1) being trained by the BO's daughter, 2) just being ridden by one or two people, or 3) just waiting to be sold.
So, around 30, possibly 40. =]
I don't have a horse, but the place I ride has a 50 stall barn (I'd say about 5 of the stalls are empty or used for hay storage). There are also 3 or more big sheds with a lot of stalls (maybe 15 per shed?). I believe that are used to temporarily store polo ponies during matches or practice (since each player will have up to 6 ponies). So probably 45 permanent residents but many more temporary residents during polo games. My trainer leases half of the barn, so probably 20-some horses are either his or his client's.
I grew up riding at a much larger barn, and I must say I love riding at a place with so few horses (especially if you consider that my trainer is only responsible for 20 or so). It just feels more personal. He has gorgeous horses too (trains and sells German sport horses) and I'm hoping to lease one someday (or that he lets me ride one or two of his for sale horses once I get back to my previous level of riding). Even his school horses are gorgeous and talented.
Ok at the barn I board Dallas at it can hold I think around 50-60 horses, it's not full right now. There is plenty of turn out space, and there are two barns. An indoor arena, outdoor arena, trails, a wash stall, a lounge, and two cubby areas(Each boarder gets a cubby to put there stuff in.).
And at my house we have a two stall barn and a good sized paddock.
We have 17 horses at the barn I board at. I own one, my friend has two, there are 7 that belong to the owner or his family (daughter, nieces), and a few that are being trained for cutting and then will go on to show. So it's small and very family-like.
There are 19 horses where I board, 5 are the owners, one is her daughters, and the rest are boarders. There are 26 stalls though and 14 paddocks. Three of the paddocks have lean-toos but all of the horses come in at night. It's not huge but it's not too tiny either, everyone for the most part gets along. I really love it :)