From experience, part time / contractors for early stage startups are usually counterproductive. They just won’t be committed, loyal, and giving 120%, while incurring massive management overhead. Don’t believe I’ve ever seen a success story.

Proper full time employees or don’t hire at all.

100% this. Also contractors are not going to wake up at 3am to fix a customer issue. The equity/responsibility that a full-time employee has is the best alarm clock.

If you are paying them for 24/7 on-call, they will.