There's no one specific answer. Some are great, others are horrendous. As a franchise, it will depend on which particular one you mean. Back in Changchun, we had 2, one great, one sucked.
You're going to hear lots of negative, here's a positive:
One of the things that will happen is that you'll have access to lots of modern equipment and books. You will also become a better teacher quickly which is good if you want to do more than a year of this. They have plenty of social events coupled with many long working hours means little down time. Usually the classes are not too big compared to other private schools.
Your "happiness level" will depend on what you want too. If you want basic pay and minimal hours, then bad choice. If you plan to develop and are willing to sacrifice personal time, go for it