I understand why people would want to lease or 1/2 lease a schoolie, as long as it’s a horse they want to ride and the barn/horse owner thinks it’s a good match.
Barns can set whatever parameters they want. If they have show quality schoolies, some require it for showing. Many barns have found that it’s a great way to offset not just care and maintenance costs. I work in a tack shop and am amazed by the stuff people buy for horses that they don’t own! Part leasers are buying bridles and leather halters with nameplates and high end half pads, sheets and blankets etc. Now, many of these people will take the equipment on to the next horse or one they eventually buy, but the barn has use of it or the equipment it frees up.
If you have a horse in full training who is not yet “ready” for you but want saddle time without the investment, a 1/2 lease makes sense. As for the price, typically it includes about 1/2 the price of standard board, plus the lessons purchased (most require lessons continue) and any extras they owner wants to include. The last part is where misunderstandings can arise. It is not unfair to ask when the lease says “shoes” or “basic veterinary” what is included and what it will cost. My old schoolie lease had great feet and only wore front shoes and required minimal farrier attention. A fellow client leased a lovely mare with the worst feet who had to be shod by the “best of the best” farriers and was done far more often. Her bills were far higher than mine.
Similarly, get an idea what happens if your lease horse is sick or hurt. Will you be allowed to ride something else if he has an abscess or gets Lyme? Will you be on the hook for treatment costs? If no other suitable horse is available, will you have to pay the monthly fee even if you can’t ride? It is always your right to find out up front what your expected monthly bills will be and the term (month to month, quarterly etc) before signing a lease of any kind.