Looking for bike ~$50

Looking for a new bike to swap out as my current one that I got second hand takes me more work to ride and has been requiring me more maintenance. I am looking for a bike that is quick, mainly just for campus use, and for short person (I am 5'1). If you are moving out and trying to get rid of your bike, please let me know. Just willing to spend around $50 since I have already bought one bike.