You also can't forget the cost of shoes (or trimming), vaccines twice a year, teeth floating once a year. The cost of those things varies by area, and who you decide to use, but those are fees that will also have to be paid regularly. It sounds like you've done a good bit of research on places to board, and boarding prices, which I'm excited to hear, but you also do have to be prepared for possible emergencies, and buying tack that fits the horse you buy, so your parents need to know that, and be willing to spend that money as well. I think the price is middle of the road depending on where you live. Here in Cali, I pay 225 a month, (no lessons), they feed my horse who's in a paddock with 3 other horses, clean the paddock, and water bucket, and do checks throughout the day. Its $400 a month for a barn stall with run, feeding, cleaning, and shavings. If you go down to Del Mar in my area, you can spend between 5-800 a month, for a stall at a show barn. One place I looked at did not turn your horse out, they just fed, cleaned stalls and waterers, had an automatic fly system in the barn, and shavings.