Seeing as this is kind of a niche market, I wouldn't get your hopes up for more than a few odd jobs through something like 3dhubs.
Do it for fun, experience and to help people, because you'll end up depressed if you try to do it for a profit.
I have a small business which I run with my girlfriend, we hand make jewelry and I handle the 3d printed stuff.
Some items are fully 3d printed, and there's some minor internal stuff I print for non-3d items, like settings for odd-shaped crystals.
If you want to make money, this is how you'll have to do it. Your own designs printed at your own pace with minimal downtime.
I've had the printer coming up on a year now (printer's been printing products for sale maybe 3-6 months of that) and It's generated revenues of maybe around 8x it's cost so far.
Granted, I've spent a lot on PLA, upgrades, replacement parts.
Most of the time was spent printing prototypes and fine tuning models to print consistently, as well as assembling the items.
So in the end, if you compare that to a normal job and the labor and materials involved, it kind of just breaks even.
The only thing that's worth anything is the designs. So unless you're getting paid well to design for clients, don't expect more than to break even at best.