I want to buy a used MacBook!

I have an ASUS laptop computer but it is too old, and my keyboard was broken for a long time, so I want to buy a new one, but I just want to a laptop work at home, few time to use, and I never play computer. I heard macbook is a good choice, but its price is too expensive, so I decide to buy an used MacBook, where to buy and how much? Give me some advice!

Thanks!