In China, anything seems to go.
I understand what your saying, many schools treat you the way they want.
one of my friends in China got ripped off, did not pay him, in fact I have heard stories from others who were not payed.
the visa bit is a laugh, because according to some schools it is ok to work without a work visa, they are the ones who like to be in control.
always best to look at the contract, I mean take a long close look, because many so called contracts are not worth the paper they are written on.
you may do OK if you like to grovel to some of these people, but in the end your just another western teacher and there are always other
suckers willing to take a chance, I said suckers because many of us are. because we put up with all the crap that is preached to us, just like many of the students. It's all about money !!!
one can imagine what is going on in the heads of some of these owners who simply abuse and cheat others.
my advise to you,
don't trust no one, look at the contract, if anything is not sounding right then don't bother.
look up schools in your browser, ask those who have been in China a while.
you can do some research of your own first, then you will have more information.
schools pay you monthly, full, or part time, but like I said, it is always possible you may not get your hard earned cash.
your in China, then you must think like a Chinese, there a some schools that treat teachers more fairly, but look on the forums and you will soon find there are many that do not have a good name. steer clear !!!!!
I'm afraid I would say a big polite no.