Cheap, steep and HOT. If you find the right place it's nice. Has all the CA issues, no rain in the summer so hay is necessary and expensive, lots of zoning and other rules and regulations, it's right outside the Napa Valley and the heart of wine country so any flat land the price will be affected by competition from wine grapes. If it's too steep for grapes it gets hard to keep horses as well. Volcanic soil. Grass is sort of sparse.
Your friend needs to visit before she falls in love with the idea of the place. The roads out there are not much better than they were when they were stagecoach routes, just have a coat of asphalt.
Thanks. I think they'd be happy with any place in California that had pretty views, affordable ish land and no snow. They are also thinking of the Lompoc to SLO area, where they said they've seen ads for land in the 10 k an acre range for 50 plus acres.
CA has some brutal terrain in spots. If the land is inexpensive it's possible it's pretty steep or miles and miles from anything. I went out to look for a place once that had five near vertical acres. The house was hanging on by its toenails in the one spot they'd carved out with a bulldozer. That one was south of Clear Lake, maybe 50 miles from Pope Valley.
My friend boards her retired horse at this beautiful retirement boarding facility in Pope Valley. Beautiful area, a tad remote (20 minutes to a small grocery store; 45 minutes to a decent size town). Your friend might contact the owners of Rockridge Ranch and talk to them. They are big time jumper folks from the SF Peninsula and live in Pope Valley part time.