Depression, anxiety, and jobs

I have depression and anxiety. I'm not social. I'm 19 years old and I've never had a job before. I know everyone has to start somewhere but I'm do scared. I'm not good at math so I'm terrified I'll not count money right. I'm also terrified that I'll forget what to do on the computer. (Only opening is cashiers). My family doesn't have a lot of money so everyone thinks it's a good idea for me to start working. Has anyone had these same fears?