i'm only 21, but i've always had a job since i was 15 and they've all been customer facing roles. sometimes it's a bit difficult but it's fine 95% of the time as most of what you have to say to each customer is the same. i've had the occasional person be rude to me and look at me like i'm dumb when i'm blocking on a word but i just act a bit sad and apologize for inconveniencing them with my stutter and it's usually enough for them to be embarrassed for being rude and apologize and/or shut up.