I don't hold checks, or ask them to be held. I do, however, sell horses on very easy terms. I'll sell a horse for a certain amount, and let the new owner pay $50 to $100 a month (whatever they can afford). I make them sign a written contract, and keep all registration papers until I'm paid in full. I have had to take back horses on a couple of occasions, but never had any problems. I have had buyers pass my name around, though, and sold more horses (for cash and on time) because of it. I won't sell like this to anyone out of driving distance from me - in case I need to get the horse back. The horse industry is much different than the cattle industry, though, and not sure that I'd do the same on a bull or cow.
When I show up to buy livestock I always bring cash. There's no point in making someone feel awkward about taking a check. If you are serious about buying then you should have the green.