The Pope, I'll put in my 2c.

You should be able to get that bike for the price quoted on Taobao, and be fairly safe. Mostly Taobao is a safe place to buy with most sellers with history, and the penny has generally dropped that sending what you should be sending for the price quoted in reasonable time is the best way to make money in the medium to long term. Given your location I'd be tempted to get the bike sent with Chongqing plates the dealer can supply, probably real for that price as around my area they are about 400 yuan, if you decide this route, take the documents to the local Gong An, if they are fake send the whole bike back. That means effectively you're insured for a year and can transfer the bike to local plates if possible, although very difficult without the original persons ID. It's not good after a year, because you need the ID of the person the bike is registered to if you want more insurance.

I don't think TB-Racing is being very helpful with his comment. Many people on here who live in SH and BJ seem to have a zero tolerance for people who are not 100% legal. The reality is 99% of Chinese riders aren't legal. Does it mean you should copy them and openly flout the law? Please no. Or talk about being illegal publicly? Also please don't. But being 'as legal as you can be' is the best policy. If you can get a license you should, if the bike can be plated and insured, it should be.

Really though, many of the laws in China are unreasonable, and it seems that the desire is to keep everyone somehow illegal to keep them in their place and have power over them
A few examples of unreasonable laws....

-You should drive a car at 20km/h through a village. It's unreasonably slow, therefore is always ignored.
-The drink drive limit is zero, not even one beer?
-Foreigners with home licenses cannot use them in China, even though their home driving standards are far higher than China's.
-You can legally buy a Yamaha R1 or Ducati, but you MUST ride it on the sidewalk or cycle lane. And give a bureaucrat one for free if you buy one.
-Complete motorcycle bans in cities and on freeways.
-If you are Chinese it's illegal not to love China.
-Empty intersections with very low traffic levels have lights and cameras.

It's hardly surprising with so many ridiculous and unreasonable laws that people then pick and choose the laws they wish to follow.