Any horse can be trained to pull. If the horse was started under saddle correctly than they should be familiar with ground driving. The big adjustment would be the harness and the weight of something. That said, the harness is an easier adjustment than the weight.
If you have never driven a horse I would look into driving lessons for you before you start your own horse. There is in my opinion, a great benefit to knowing the equipment and what is "appropriate" behavior when driving as opposed to just buying a harness and learning on your own. If you have/find the local driving society (a google search would bring it up) they should have a lessons section. It would be best to take lessons with your horse. Like anything else, green and green = black and blue.
No matter what you do, do not attach your horse to any object without the appropriate equipment. This means don't tie lines to the saddle and have it pull you on a sleigh or sled, like wise for attaching a long line to the halter.