I can't speak to franchising, but I know two people who have opened up sports performance oriented gyms. It took A LOT of work. I think to be successful in this you'll need to find a niche where people will pay a premium. For example, I'll describe a weightlifting gym, as in the sport of weightlifting (not powerlifting, but kind of the same thing). People will pay significantly more than a big box gym if they know they have access to platforms and boxes and can drop the weights and not have to deal with someone doing curls in the squat rack, BUT, are there enough serious lifters in your area for this? Do you know what equipment your clientele wants? A power lifter would be pissed you didn't have yokes and stones, a weightlifter would be pissed if you didn't have enough change plates nearby. Neither of them would care if you had 10 Woodway mills.
Group fitness is popular, and probably an oversaturated market, or at least it was a few years ago. At that point you're almost just trying to create an entire brand, which isn't easy. I saw someone try and fail at this, hard to watch.
You could do a general "sports performance" gym. I used to work at a place like that. You can charge out the wazoo for membership and classes. Do things like a "summer junior high soccer camp" where kids meet 2–3 times a week for a few weeks, $150 per kid, get 20 kids, that's $3,000. Do a few more classes and you're making decent money. The owner was a pretty talented PT. He had a million certifications, but anybody can get those. The proof is in the pudding, he made athletes in many sports better, and it was obvious. Can you do that? For most people, the answer is no. But, you could try to hire PTs. Again, a million certifications are nice, but almost anyone can get them. You need trainers with a history in sport and injury prevention, not just meatheads.