This is something I'd insist on paying for. Investment in a relationship like this goes both ways, and having a coach that was not incentivized to continue would be a deal-breaker for me.

The problem is this. Any coach who you want to listen to can make more programming for themselves than you can afford to pay them.

Getting the incentives right is tricky. Money is often not going to be the right incentive here.

I agree, money isn't the only incentive. Some people (myself included) have a passion for teaching. Money is just an extra motivator.

I don't think its true that they can necessarily make more programming themselves than I can afford to pay them either. Remember, I am not wanting to hire someone full time, but for only a few hours a week. If I have to pay multiple hours of wages for an hour of high quality coaching, that is perfectly fine with me.