I would think a fair price for a personal trainer to charge is $40 per hour. Figure on a 2 hour session, 3 clients a day, 4 days a week.
Groups are more efficent, but the money is in catering to the rich and beautiful (or those who have the $ and want to convince themselves they are beautiful).
Marketing is crucial. Don’t focus on health. Keep the emphasis on looks and energy. Those are words that get peoples attention.
If its practical, get them to meet you in a park, so they can see what goal they are aiming for. Nothing motivates a person like the competetion!