It definitely depends on your area, along with the quality of board and training.
How much does similar boarding cost in your area? I'd expect to spend a minimum of $300/month in my area for full care including hay and feeding owner-supplied grain, though most places are closer to $400.
How often will you be working with the horse? I've seen full training range from being worked 4x weekly to every day. You want to make sure that you're getting paid reasonably for the time you're putting in, and that may vary based on what you consider your time to be worth. Averaging 30 minutes a day (or 1 hour every other day) would be about 15 hours and is probably at the low end of the amount of time you'd actually spend training the horse. If you paid yourself $20/hour, that would add up to $300. So between board & training, I'd think $600 would be a minimum starting point based on prices in my area.
$30-40 would be reasonable in my area for a 1-hour private beginner-to-intermediate riding lesson. Since it's pretty close, I wouldn't charge any extra for mileage.
“The horse is a mirror to your soul. Sometimes you might not like what you see. Sometimes you will.” - Buck Brannaman
"Nothing forced can ever be beautiful." - Xenophon