I have a couple of Kioti tractors, and I think the DK50se HST I have is just about the perfect tractor for a horse farm. It's 50 HP, so probably a little bigger than required unless you're looking to make your own hay or your property is hilly. I use it for everything - dragging paddocks, pastures, and the arena, dumping muck tubs, rototilling, mowing, brush hogging, making hay, loading the manure spreader, snow removal, logging, you name it. I've experienced almost no problems with it, and I'd had it for almost 10 years now. it gets used almost every day.
And yes to HST, definitely. You'll use the loader more than anything and an HST transmission is ideal for that.
And also yes, if you finance with Kioti at 0%, you're basically going to pay the interest up front instead of getting a cash "discount", but it still works out to a pretty low rate. I did that with my RX7320 - 0% down and 0% interest for 6 years, and the APR worked out to about 2.5% which I was OK with. Seemed like a pretty cheap way to spread the cost out over a few years, and meanwhile I've invested most of the cash I would have spent on the tractor. So far my average annual return has been much, much greater than the cost of the "interest" on the loan.