Just to clarify what you're looking for ... You need an equal to bounce ideas off who can't steal your system?
From your opening line it seems you want someone with roughly the same skills
So I need someone of roughly equal capabilities to bounce ideas off.
Surely you can do that yourself? And instead save the 50% equity for someone(s) who has vital skills you lack.
It's what I'm doing currently, but realized it's very inefficient working on it as a side project with a full time job. What would take me 1-2 days of intensive, full time work, can take over a week due to having to spread it in small, scattered patches, when I find time after the day job.
So to increase efficiency I could:
a) Quit my job and concentrate full time on developing a successful trading system.
b) Take a part time job, and use half of a working day working on my trading system.
c) Keep my full time job but hire someone to do #a instead of me.
#a is the most risky, I'm not going to pursue it soon.
#b might be an alternative, but still not something I'm gonna jump on very soon.
So it remains #c.
The key ingredient is that for #c I need someone able to concentrate full time on trading strategy research. They also need to have similar level of qualifications, so we can discuss quantsy stuff and split the work. And I'm aware that $1k is not a particularly compelling amount to live on, but it'd be enough if the reasons driving this hypothetical unicorn to work full time on trading strategy research were the same as mine. It would be a lot like option #a from the guy's perspective.