I did this last year. I work full time for ~100/hr, and someone I've worked with before, recommended me to an early stage startup in the US. They paid me ~130/hr just to be part of the meetings with their EU based dev team. Monthly I was making 2-3k extra but the context switching, startup rollercoaster, dev team not performing turned out to be stressful. In the end they secured funding and assembled an in house dev team, so they didn't need me anymore. I suggest you try it, but not for the extra money because the extra stress is not sustainable long term, do it for the learning experience and maybe that will help you in the future.
tried both full time and contractor years back, too stressful, can't deal with both with kids, I since focus on one of them, not both at the same time, for the sake of my own health.
By full time with 100/hr I meant that I'm a contractor working for a company for 40hrs a week. Since we started to work remote I picked up a second assignment of a few hours extra a week. But all in all it becomes more stressful.
Unless both jobs are doing very similar things on the tech stack(so our brain does not context switch too heavily), but they're not competing in the same market(an ethical issue), I might still consider it, the chance is too low, so far I do one job and I actually can have a life.
