Don’t call it “part time”, become an independent contractor, focus on a niche, and only bill how ever many hours you like. I have spent long periods of time only billing ~3 hours per day. Great for life/work balance. Btw, the more you bill the more your time will be valued. Don’t make a concession, mark yourself up as premium.
Even better, charge for entire projects or engagements, start to finish. The more competent and efficient you are, the more you will make per unit of time.
Integrity and foresight are the “premium.”