"and doesn’t feel right taking a slice of someone else’s pie"
I hate to say it, but you need to get over that. This very mindset has screwed me over more times than I care to think about. I'm in the $2B+ generated revenue part of my career. I've got a lot of scars, bruises and broken dreams that brought me here. Built an entire start-up, that sold for $256M, got screwed out of $2M. That was on the low-end of what I've lost in various endeavours. And I have stupidly made that mistake several times. Over the years I've learned some hard lessons.
I now take the approach that "I charge this much per day/week for my time, if you cannot afford that and wish to give me equity in lieu of (some of) my pay, these are my terms." And I don't do 4 year vesting with 1 year cliff. If I am taking a significant pay cut, e.g. 60% to 70% from my usual day rate, the cliff is 90 days on an accelerated vesting schedule. And it is a grant, not options, I'm not giving back money to get what I earned.
You also need to start negotiating your contracts to have a quaterly or bi-annual rate increase from "I'm doing you a solid here with a big discount" so that three years later, after built all the tech for the start-up, you aren't earning less than the Junior who struggles to remember the difference between margins and offsets. On client discounts (I've stopped giving them except where large chunks of equity are concerned), you can backload them too, so that should the client cut you loose because you bumped your rate by 10% last year, as stated in your contract, they pay a termination fee. Some clients will balk and nope out, those clients you don't want. It took me decades to figure out I was allowed to say "no" to potential work.
Right now I am charging less than what I have in the past, $1,000/day as opposed to $1,600 to $2,000/day, because I need some stress free time, and at 6pm, I turn off my computer and forget about my work.