In another life, I worked for my current employer (call center) in a part-time capacity while I had a different day job as an accounts payable wench.
If you find the right call center, it can be a great gig. Obviously, there are sales-centric call centers, and service-centric call centers (and probably tons of others in between.)
I was never comfortable with Sales, and I work for a service-centric call center. The company I work for has gone through many changes in the 10 years I've been there, and not all of the "perks" I mention are still in place at my particular employer. But, a lot of the good stuff I mention can be found within the industry, if you're willing to do your homework.
In addition to some flexible hours (especially if it's a 24/7/365 call center) it's not entirely uncommon in the industry to get differentials or bonuses for certain shifts (let's face it, the career-folk in those industries are looking for the 9 to 5 shift.) And, in some cases, you might also get a bonus based on quality of calls/no call outs (my org no longer does this; but in its heyday, they did, and my $10/,hr quickly jumped to $15/hr based on the number of hoours I worked - in my org's case, you got the same bonus regardless of number of hours worked. That's some sweet moolah for a part-time gig.)
Another perk could be the ability to easily move (facilitated by either working for a company with a location in your new locale, or, in some cases, telecommuting, both of which keep you flexible if an SO or roommate gets a great opportunity elsewhere, as was my case. Eternal summer in SoCal sounded like a magnificent trade-off for New England's crummy winters, and not having to sweat what the heck you would do for "essentials" money once you get there definitely makes that kind of decision easier.)
And, of course, opportunity for growth. I leveraged my part-time, front-line position to a salaried management position. Most of the hands-on roles in a call center thrive on internal hiring. I will tell you right now that as a hiring manager, I will give precedence to the person who's been working on the phones for the past 2 years before the person off the street who has 10 years' experience "managing customers." While there is a lot of diversity within call centers, a fair amount of them draw from the same small pool of call platforms - and having working knowledge of what they can do (and can't do) from being on the front lines trumps 5 months of non-call handling education every damn time.
There are definitely some cons. The *biggest* one I can think of (admittedly based on the things that irked me when I was pulling the gig on top of a full-time job) is that, if you're dealing with a more service-centric call center, holidays are a must. If you're doing this on top of a full-time job, and banking on those company holidays to spend time with friends and family, you can kiss at least some of them goodbye. Managers will do their best to honor requests, but if you are low person on the totem pole, and/or that day of the week is within your normal availability, you can expect to work (though, volume is generally down on such days, so it often isn't a full day. Managers usually try to share the pain those days, and schedule people normally available on the day of the week the holiday falls, but for a half shift. Personally, my experience was always that those days were the best - I never felt more "community" than working Thanksgiving or Christmas, and knowing we were all in it together, and so help us, we would have some fun! Also: holidays frequently means at least time and a half pay.) Similarly, you can expect to be required to work at least one weekend day/night a week. If you go into it expecting that you can give 5 weeknights of availability and no weekend availability, you likely won't get hired (or, if you do, you won't get scheduled to the maximum number of hours you said you'd be willing to work, because you don't have availability when it's actually needed.)
In the end, call-center gigs can be a great fit if you have a lot of flexibility and if you don't care about traditional holidays. You have to weigh the pros/cons, do some homework on the organization if you are considering one, and make the ultimate decision for yourself.
