I also think you need to start your horse training before getting your cart. If your horse doesn't take to driving, you have wasted a lot of money on a cart. It was Lilly that was well in to driving her horse when something happened. Still trying to find out what, for a learning reason.
There is a lot of training that comes before the cart purchase.
Some driving clubs in your area:
Arizona Driving & Carriage Society
25375 N Feather Mtn. Rd.
Paulden, AZ 86334
Phone: (928) 636-4228
Web Site: ADCS Home
Primary Contact: Mary Jane Atonna
Grass Ridge Equestrian Foundation Inc.
PO Box 141
Sonoita, AZ 85637
Phone: (520) 455-5093
Web Site: Grass Ridge Equestrian Foundation
Primary Contact: Leonard Anderson
It is best to find a trainer or a mentor to help you. Put an ad on craig's list to see if there is another driver around.
Don't use a check rein, and stay away from a trainer and/or mentor that insists on one.