3 sentences

1. 我有个中间人。

   wǒ yǒu gè zhōng​jiān​rén.

   I have a middleman.

   Source: OpenSubtitles

2. 买卖双方通过中间人达成了协议。

   mǎi​mài shuāng​fāng tōng​guò zhōng​jiān​rén dá​chéng le xié​yì.

   The buyer and seller reached an agreement through a middleman.

   Source: Dong Chinese Dictionary

3. 按照惯例，这笔交易的中间人可以拿到一定比例的回扣。

   àn​zhào guàn​lì, zhè bǐ jiāo​yì de zhōng​jiān​rén kě​yǐ ná​dào yī​dìng bǐ​lì de huí​kòu.

   By convention, the middleman in this transaction gets a percentage as a kickback.

   Source: Dong Chinese Dictionary