Squire Affinity P-Bass Body w/ MIM P-Bass Neck?

Welcome to TalkBass.
Not for China specifically, but Indonesia, Japan, Korea, Mexico and USA are all interchangeable these days, why wouldn't China?

 

If it's cheap go for it!
I wouldn't see why it won't fit.
Maybe look up the dimensions for both but other then that go for i!

 

I can speak on this from experience. I've sold various basses that I've assembled from parts.
I have assembled Squier bass bodies with MIM Fender necks and have not had any problems.
If you can get it cheap, it is well worth the gamble. Besides, even if the holes don't line up
perfectly, well cut dowels can solve the problem.

 

I never had

I never ran into those issues.

 

Here's the simple answer: Neck-to-body fit, yes. Neck screw hole placement, possibly not. Here's the simpler answer - get the neck, if the holes don't match up, fill them, redrill the pilot holes. No problem, especially at a steal price.

 

My MiM Pbass neck doesn't fit particularly well into my Squier Pbass body. There's a fair bit of gap on all sides of the neck. YMMV