2 sentences for 便宜 (pián​yi — petty advantage)

1. 他总是想占别人的小便宜。

   tā zǒng​shì xiǎng zhàn bié​ren de xiǎo pián​yi.

   He is always looking to gain small advantages at the expense of others.

   Source: Dong Chinese Dictionary

2. 他这人做事很刁，总是想方设法占便宜。

   tā zhèi rén zuò​shì hěn diāo, zǒng​shì xiǎng​fāng​shè​fǎ zhàn pián​yi.

   He is very tricky in his dealings and always tries to find ways to take advantage of others.

   Source: Dong Chinese Dictionary