The things said here can be true, but can be VERY relative depending upon where you are.

A great many schools simply will NOT send an air ticket. It doesn't mean they're dodgy...at least not too dodgy. ALL schools in China are dodgy one way or another...
There are a lot of dodgy schools...and a lot of dodgy would-be teachers. MANY people accept jobs here, and then simply never show up. This is why most schools won't front the air ticket...it's actually somewhat justified.

4500 RMB a month is enough to live on...in the hinterlands. You'll die on this salary in Beijing or Shanghai or most of the cities in the prosperous area around Shanghai. (Where I live, near Shanghai, that bowl of mixed fried rice is more like 10 RMB...) Even in the sticks, 4500 a month won't be much fun. It won't leave much for traveling or saving or going out for a good time. Why exactly are you coming to China, anyway? I can't recommend a salary under 6000 anywhere in China unles you're teaching at a university. (Uni salaries are regulated by law, and generally offer shorter hours that make part-tim work possible...)

Be careful of broad-brush descriptions of China. What's true in, say, Kunming may not be true at all in Ningbo or Taiyuan or Dalian. Get SPECIFIC information...if you ask long enough, you'll find what you really need.

Raoul (BBQ, PBR, 6UL.Dv8)
Raoul's China Expat Saloon
http://chinateachers.proboards17.com
Nate's China School Review
http://www.chinaschoolreview.net