In my eyes, in this situation you are either looking for a co-founder, and give them equity accordingly, or you treat them as an investor who happens to "invest" with work.
The former means giving more than you would to an "employee" and giving shares rather than options, and giving them a real say in the business.
The latter means going to people like me who earn well enough from consulting etc. that we can afford to spend some of our time on startups without getting paid in cash fully knowing it's a high risk thing, and who will insist on seeing your cap table and investment prospectus so that we can judge the risk, and who will insist on terms that provides additional security.
Note that in the latter case my first question would be "why haven't you been able to find an investor yet"?
I've talked to people who have had convincing reasons, but I've also talked to people who presented me with investor decks where it took me 5 seconds to see why they'd failed to secure investors.
Personally I don't think devs who are inexperienced with startups should consider those kind of arrangements. For me it's kind-of a fun gamble that I take on the side of making more money than most from my paying clients - I expect most of the won't pay, but that's ok.