Experiences may vary, but I was also able to finance the purchase of two non-Kubota implements through Kubota Credit Corporation (KCC) when I bought the tractor. This, of course, is dependent on both the dealer and KCC agreeing that your Kubota purchases were sufficient.
Someone may have mentioned it already, but KCC generally asks for proof of insurance for the equipment financed. Your homeowners or an umbrella coverage may be sufficient. Otherwise, you may want to shop around ahead of time or be stuck with what Kubota offers.
Finally, in my very short time of visiting tractor dealers, I've found that the financing incentives were not available during the winter, but that prices were much lower for many of the most common attachments. Don't know if tractor prices are as cyclical.