Sign up and Take on

Sign up verb - Engage by written agreement.

Take on is a synonym for sign up in use topic. In some cases you can use "Take on" instead a verb "Sign up", when it comes to topics like hire, gather resources, give money in exchange for work performed.

Take on verb - To provide with a paying job.

Sign up is a synonym for take on in hire topic. You can use "Sign up" instead a verb "Take on".