The hard part is finding appliances that need fixing. This is super easy if you happen to own a lot do things that break. If not, it becomes quite boring and tedious to scout out things that are breaking for other people, that you have no personal motivation to fix, to get the broken appliance and then figure out the 3d model for the bad part.
It's a neat business model: The person posts DIY repair videos on youtube, which drives traffic to his site. The strollers can easily cost $1000 new, and are often handed down / resold, so there is motivation to keep them running, and they have some weak spots which tend to break. The 3D printed replacement parts can be of superior quality to the original parts.
It seems like once you build up a critical mass of reputation/SEO you could get people to send you their broken parts to reproduce (then start advertising that specific part too)
Then that depends on either how much they're paying for the part and how much you enjoying 3d modeling and the trial and error dof 3d printing. You'll also need at least a real version of the part to copy and maybe even the appliance.
If you buy a bag with rollerblade wheels vs the plastic castering garbage that comes on a lot of bags you’ll get significantly more life out of them. I spend 15-20 days/month on the road and get several years out of rollerblade wheels.
