Every studio is different. Some studio owners train their own staff, some use staff to train staff, and some hire teachers from the outside. The worst studios provide almost no training, and instead send their teachers into a room with a video... but those are few and far between these days. If you do get training, it will more likely be in the form of group classes, but at least the classes will be small. Any private training will more likely be from a staff member, and will mostly consist of syllabus steps. It's very expensive to hire a professional teacher from the outside, so don't expect any major high calibre training that will improve your technique.
Your training time will be divided between dance and sales training, and in all likelihood, the sales training will be the majority.
Dancers who are serious about improving their craft do not rely on studio-funded training. They finance their own education, typically taking lessons from high-calibre teachers on the outside. This can be difficult on a chain studio salary, but if you're a popular teacher with many students, you can pull it off.
No matter how you earn money, through the teaching of dancing or otherwise, you can always improve your dancing by paying for your own lessons. So your decision to join this or any chain studio should not depend on the quality of staff training they provide. Still, if you're curious, the best way to find out is to go straight to the source... ask the studio owner or manager.
Regards,
Jonathan Atkinson