Some years ago, I was growing weary of the hour-each-way commute to work I'd suffered with for over a dozen years. So, when I heard about a trade show company opening up minutes from my home, I contacted the owners about the possibilities of my working for them. The beginnings of this mistake can be found "documented" on this very website if you choose to seek it out. Real entertaining.
Anyway, it started out great there, and before long it turned into a very unfunny joke. Needless to say, I went through the ol' "we hired you some help, train her, and when she's ready, we'll tell you we can no longer afford you and must lay you off" routine. Didn't even make it a year. And I was let go a month after buying a new vehicle, getting married, and carrying extra debt due to those sort of things. So I went about finding a new job. I had 25 years in the industry, shouldn't be too tough.
Couldn't get back in to my previous job. And then one after another, nothing. Didn't pay much. Wasn't hiring. Will call you later. No calls at all after interviews. Began to wonder if it was my age (had just turned 50 around that time), or was my old boss dragging my name through the dirt through referrals? I don't know. But at that time I started up what would normally be called "side work", if it were on the side of a full-time job. But for me, it was just "work" (it was also part revenge -- trying to take as much small local business away as I could from the jerks who fired me). My little graphics business, run from my house. It would be almost 6 months before someone finally took me in for a regular day job in the print business.
By this time, I was hoping to just slowly grow and keep afloat the side business over the next decade or so, and have a small, established graphics shop. Something to do in retirement because I know we'll need it. Plus, I like it. That's the plan. But now I have a job that has some overlapping work, and as mentioned in many prior messages in this thread, that's not a cool thing to do to your boss.
In order to "have it all", I kept an open conversation about it with him. And I've cut out any overlaps. My day job is mostly about quantity. The owner doesn't have a lot of interest in one-offs or tiny orders (unless it's personal for friends, family, really good customers, etc.). He'd be fine if he never sold another 2' x 3' banner. So I offer those kind of things, really just locally, in a town 40 miles from here (yep, back to that long f**kin' commute again). Single banners, t-shirts, window graphics, etc. Stuff we don't do "at work". Mostly I sub it out, but I just picked up a small cutter and a hat press, and already had the garment press. I asked the boss if I could have vinyl scraps to play around with on the cutter since it was new and not a brand we use here. These are scraps we'd throw away, but I'll still always ask before just walking out with anything.
So what I guess I'm yapping about here is, don't do it on the sly. Don't duplicate your day gig (wouldn't your boss rather you brought that work to him?). Don't steal stuff. Not tools. Not materials. Nothing. And if the boss says no one of those requests even if it seems honest (like, no, I'd rather you not bring home scraps even though they always go right to the dumpster), honor it. That's all I got!