It should be 2 years or younger.
Conformation needs to be suitable for driving.
Colour-wise, I'm alright with anything, but I prefer lighter-coloured horses (chestnuts, palominos, etc) unless a darker horse has markings. Pintos are alright, but I prefer minimally marked.
I'd really like the pony to be halter-broke and good for the farrier.
I'd prefer a filly, but am not stuck on that.
In terms of the type, I'd like something less modern and a bit more stocky.
Not drafty, but not looking like a super thin park horse.
If you have or know of anything that fits these criteria, please post here with pictures or links.