THERE IS A 是不是等同于every coin has its two sides.

There is a catch = 内有玄机.
例如：他不会白白的帮你,小心内有玄机（He won't help you for nothing.There is a catch.）
Every coin has its two sides = 凡事都有其利与弊.与 there is a catch 意思不同.