I live in an area which was once very horsey, but the cost of living is astronomically high. There are many barns, but many are struggling.
Most of the successful barns tend to be show barns that have an established reputation. Getting along with people, particularly non-horsey people (parents and more hands-off owners) is useful. Unless you’re very talented and very winning, people are less accepting of the trainer-as-drill sergeant model nowadays (and a good thing, too). It seems harder and harder for people to survive who do the typical lesson barn model with school horses. Most barns in my area now seem to have one or two horses for a first-time beginner lesson and then have people part-leasing or leasing in a program (or people who own their own horses).
Truthfully, when barns begin to fail, the barn begins to skimp on costs (shavings, hay, pasture care, arena care), and then more people begin to leave, and things can further spiral downward. So not beginning any horse business on a shoestring for ethical reasons (for the horses) is a biggie.
I also know people who just have barns with their own personal horses, rent out a few stalls, have a small outdoor, and live near one of the areas where it’s still possible to hack out. But horses aren’t their main source of income, they’re people with other jobs who rent stalls to supplement their horsey habit.
I know a few lesson/riding barns with small breeding programs, but I honestly (feel free to chime in, others) don’t know how they profit by them, unless the owner has a very established reputation is a trainer and can put miles on the few young horses homebred at shows.
There are also a couple of barns that I still can’t believe are in business, but seem to attract cliques of kids who don’t want to leave the barn, because their friends ride there, and other barns that have very nice facilities and high-quality care, but have empty stalls because the main owner or trainer is such a PIA to deal with.
I think knowing your area, target market (like any business), your biggest costs, sunk costs, and your strengths and weaknesses, like any prospective business can be useful. Do the SWOT (strengths, weaknesses, opportunities, threats analysis) if that helps!