Justin, I too have not taught the subjects mentioned before, although I've done the Academic English, Business and Social Science on mainland and in seemingly similar courses as you. To the point, it's essential that your school chooses the right candidates for the courses. Otherwise, you'll be scratching your head and racking your brains how to teach them throughout the term. Cunning's mentioned the IELTS scores that are usually a good indicator how the kids are in the language area. To qualify for a respectible Uni in Australia 5.5 or 6.0 is sufficient most of the time, however, for many UK Unis 6.5 is necessary, or the kids'll have to go through a western foundation course there. Most importantly, to begin such a course as you are to teach on mainland, from my experience, students need at least 4.5 if not 5.0 in IELTS. Then, it's fairly important the candidates for such specialty courses in English need to have some basic knowledge in the subjects to be taught and a subject mock test is suggestable.

Now, if I were you, i'd first ask the school how they recruit for these specialty courses and how long do they plan to have them on. Mainlanders love cutting corners and carry out crash courses as those are more profitable and as kids' parents are so demanding too. Moreover, i'd make sure the school's got some appropriate support in terms of staff, computer access and material.

On the city of Senzhen and costs, it's a great area to work or be in, however I've heard many schools/centers lack the licensing to hire foreign experts there (do your search). Costs are quite high now there and you're gith it's partly 'cause of the vicinity to HK. Chinese food's great and if you are ok with it you may not spend much. Utilities may come up to 400-500 RMB monthly if you use too much water and in Summer the AC and then in Winter if you have a heater. Your salary offer may not be up to the local standard there as some private language mills or kindergartens pay a bit more there. So, i'd bargain further if i could. In any case, you'll be able to save some money every month as long as you don't go clubing at night.

Cheers and beers