Maybe you should suggest that they find a reputable trainer and ask if you can assist the trainer while he/she is working with the horses. That way, you can kill 2 birds with one stone...so to speak. You get to learn more about how to start a horse and the horses are given the best chance to get good training and not have a novice trainer making mistakes on them.
And, just so you know, that last statement wasn't a dig against you. I was a novice trainer once myself and I completely screwed up the first horse I trained on my own. Screwed him up to the point that nobody but me can successfully ride him. Thankfully, I was in a position to give him a forever home with me, but not all horses are that lucky. After him, I started training horses under the watchful eye and guiding hand of a veteran trainer and it's been much more fun and successful since then. Now, about 13 years later, I am successfully training on my own with my own reputation and my own customers.