I know in Shanghai man over 45 and woman over 40 makes contribution as self-employed could make half contribution for 3 years. ie. this years contribution is $200, you can make $100 this year. Next year's rate is $220(for example), you will pay $110 but no more than 3 years to get this discount contribution. Many cities have similar rule but you need to ask.
If he is old than 46, he could not make contribution even he starts now because there is less than 108 mothns for him to contribute. He can negotiate with Chinese SS to make up the contribution for past years to reach 180 months. But you will have to pay lump-sum contribution which may be expensive (I know in Shanghai is about $20,000). But you don't need to pay a penny since you have reached 180 month.
This is really depdens on your own judgement. If you think that you are healthy and live longer, you will live in China after retirement, that might be a good investment. Besides tui-xiu-gong-zi, you can claim a certain percentage of medical expense(again it varies from different cities).
It is like any commecial life insurance so make your own judgement. I am not responsible for your judgement. Call your friends,family in China and talk with them to make a wise decision. I just provide information here which might not be accurate.