Looking for a slim paperback from the 80s. It might have been from either Starbooks or Scholastic Book Club. Written at the early reader level, a little less than a full chapter book. Set in the American West. A boy goes to a livestock auction and encounters a horse who can talk. He’s a recently captured mustang who wants to rejoin his herd. He persuades the boy to buy him and they become friends but the horse always wants to return to the wild. Somehow the boy smashes his mom’s potted aloe plant, which she needs to treat a burned hand. The horse offers a deal where he will show the boy where to find one growing in the wild in exchange for his freedom. They make a secret journey into the wilderness at night to find the plant. I think the title is something obvious like “The Horse Who Could Talk” but I can’t find anything online.