Updated: May 8
While earning potential in retail, catering, and freelance varies wildly based on position, location, and demand, I would say you generally have a higher ceiling based on hourly wage with bartender (for example, my bartenders make at least $27/hr + tips or $30 minimum rate for years now). Based on my experience, this ALWAYS beats a caterer position (especially because usually caterers will not let you accept tips!) but it depends when it comes to a retail position (if you are super lucky and willing to work super hard, I have heard of retail positions with earning potential of $500+ a night).
Keep in mind, annual earning income may be different, of course, as you will not usually have steady 40+ hrs a week as you would with a retail or catering job (primarily because most of your bartending events will booked at overlapping times, so you can not appear at all of them). Regardless, the BEST thing about freelancing is that you create your own schedule, which means you can do this without quitting your daytime job (which is what I have been doing for the last 7 years!). With this business, you can truly have your cake and eat it too ;-). And one other thing you can be certain of (and this bears saying in all caps): IT IS THE EASIEST, MOST FUN MONEY YOU WILL EVER MAKE IN THE BARTENDING INDUSTRY!