We have two different questions here. For me I don't believe it is possible for a serious meditator to obtain peace of mind and make a living as a bartender. Working as a bartender is simply wrong livelihood. And in order to have peace of mind we have to have Right Livelihood.
The second question, when does Right Livelihood usually dawn on people if they are not taught the Five Precepts? We don't teach the Five Precepts, but we are hopeful that the main causes for Right Livelihood are learned in the very first retreat, because all the precepts center around Compassion. To have Right Livelihood means we are having Compassion for ourselves and for others. Being a bartender certainly is not out of Compassion for anybody, it is wrong livelihood.
Now, although we don't teach the Five Precepts, we teach what is beneath them, and that is the Compassionate Intention. When you open to that compassionate intention within yourself, you want to do things that are good and helpful, you want others to do things that are good and helpful. And there is no way that you can stay in a profession like bar tendering and think that you are going to get peace of mind in that way. So, the Five Precepts come out of the Compassionate Intention, the whole motivation or Right Intention. We don't feel we have to teach the Five Precepts. As well, on occasion, when they are taught, sometimes especially from the Judea or Christian background, people feel as if they are the 10 Commandants and you should do this and should do that. As you know we don't like the word "should" used in that way.
But when you actually open to Compassion, you are not going to want to kill, to steal, to have sexual misconduct, to use your speech in harmful ways and you are not going to want to take intoxicants that confuse your mind. So as you develop the Compassionate Intention, you automatically will keep the Five Precepts.