Shenzhen Seadragon, much like other companies, is shady as fuck.

The teacher pays for nearly everything. Initial start up costs to the teacher, 4 and 1/2 months of rental before you even see a penny come back. For which you get the wonderful pleasure of being a foreigner, likely speaking no Mandarin, to arrange your own accommodation - with little / no assistance, getting a tax free housing allowance - if you can find a landlord who'll give you the tax certificate needed for you to get the allowance tax free. (Also, you have to bring the certificate to the head office, even though you might be 4 hours away). Other costs, YOU pay for the medical, YOU pay for the visa process, YOU get fucked over.

One to avoid.