I think that it as long as everything is written out and signed, and both parties know exactly what they are getting into, and who's responsible for what, that paying chunks at a time to pay off the horse is a great way to get a horse in this economy especially without breaking the bank, and still having to have left over money for board, and vet fees, ect. Definitely decide though before signing anything, what the options are if say the horse gets injured and can no longer do what it is you want to do with him, will you be able to back out, refund money, not refund money, ect. Have an end date as well, and if he gets paid off sooner than great, but at least you are working towards a goal of a date not just an amount of money. My bf bought me my Arab, and I'm slowly buying him out of her a month at a time, so that I can do with her what I want, since the original plan to train her a bit, and either sell her or lease her isn't working out so well. I've gotten to attached to her, and due to problems of tack fit and stuff (all my stuff was sized for TB's and WBs, and she's not exactly that big lol, training is taking a lot longer than expected. Good luck.