What is the proper way to look for a second job without stepping on my current employers toes?

I have worked at my current job for five years. I've been working full-time since I graduated high school. My availability for them has always been wide open. I work ALL shifts - mornings, afternoons, evenings, and overnights. I think it's good that I've been flexible for them, but I also think they might be too used to it. I previously tried joining a choir and asked for Sunday mornings and Tuesday evenings off, and they were reluctant to even work around that.

I'm at a point right now where money is pretty tight and the only reasonable solution I can see is to get a second job. I work 40hrs/week at my current job. I figure that I'd only need 8-16 hrs/week at a part-time job.

I told one of my supervisors that I am looking for something part-time just so they don't get a surprise reference call. She said she'd talk about it with my other supervisor. I don't think I gave her an option though. She hasn't said anything about it since. Should I just go ahead and start applying?

If you have been the type of employee that you indicate then your current employer would be foolish to let you go.

You have already told them you are looking for a second job, so you have done your part. While looking for that job keep the possibility open that you might find another full time job to replace the one you have.

When you find the other part time job, go to your boss and tell them that you enjoy working there and hope to continue but have been forced, for financial reasons, to take a second job and that you will need some flexibility when it comes to scheduling.

If they have a problem with that then you need to find another full time job for sure.

Why are you going to go through all of that nonsense and not just look for another job that will pay you better wages? In fact, I would be looking to leave your place of employment. You have been there 5 years and always been flexible? Your a dream employee! Now they can't help you out? Screw them. Get out of there and find a better paying job. I would be shocked if you found a second job who would willingly work around your other work schedule.