I've always kept my horses in pasture, without access to stalls at all. However, the pasture has some natural shelter. I don't clip my horses at all (I'm in Canada, though, so maybe this would be less of a concern for you).
You should look for shelter (natural or man-made). Even trees or coulees can work. Fences should be in good shape. No junk in the pasture, such as loose wire, of course. Fresh water source that's relatively clean. If horses will be in seperate, but adjacent, pasture, barbed wire fence is a bad idea. In fact, any type of wire may be a bad idea in that case.
Do you turn your horse out with a halter on or anything else he could get hung up on? If so, you might want to rethink this practice, or at least look for pasture free of stuff the halter could catch on.
The other thing you'll need to be aware of is grass founder. This is most likely to be a problem if it rains after a drought, and in summer when the grass is really lush and high. Some horses don't seem to be prone to it at all, but it can easily cripple other horses. At any rate, you'll want to ask your pasture manager how she gets around this. I'm just finishing up an equine nutrition course, and one strategy is to cut the grass, or hay it. My horses are on a ranch, so I think next year we'll keep some cattle closer to home, and have the cattle graze the pastures a little before sending the horses in.
Anyway, those are just a few thoughts off the top of my head.