Trust is a problem
Think about the last time someone on the street asked you for money or to sign a petition. You probably tried to avoid eye contact and kept walking, right? Even if you stopped to engage, you felt deeply uncomfortable. The cause of your discomfort probably isn't that you dislike the person's cause, it's that you don't know them and instinctually don't trust them.
You might think that your startup idea and business plan are so strong that people should be falling over themselves to work with you. And that might be the case! The reality is, however, that no one will work with you until you build trust with them.
Build your network
This one is obvious, so I'll be brief: think of networking like exercise. It's painful to start out, but as you do it consistently it gets easier and the results really start to show. Reach out to a former colleague and take them to lunch, ask them what they've been up to and mention what you're working on. Keep reminding people that you exist and they'll think of you when the time is right.
Show them proof
Suppose you get lucky and meet a developer who could help you make your idea reality. Just pitch them on your clearly amazing idea and the job's done, right? They'll spend the next 3 months building what you need and we'll be cashing investor checks in no time!
Here's the problem: every developer already has a long list of startup ideas of their own. If their only compensation is equity then why wouldn't they just spend time working on their own idea that they love (and that they get to keep 100% of), rather than take a fraction of your idea that they're ambivalent about?
If you're going to have any chance of getting a developer to agree to work with you then you need to have proof ready. Here's what proof looks like; you're going to need several of them:
Social: they know and trust you or you have a reputation that precedes you
Traction: you have customers signed on and market research you can share
Track record: you've built, grown, and exited a startup successfully in the past
Domain expertise: you have spent years on the problem domain know the problems to solve
Complementary skills: you have sales, marketing, and operations expertise
Skin in the game: you have invested your own money towards making this a reality
Equity-only has tradeoffs
If a developer agrees to work with you on an equity-only compensation basis then be prepared for disappointment. Sure, you've lowered your risk and might even be able to bootstrap this thing, but the tradeoff is that your partner almost certainly won't be as passionate or dedicated as you are. Take care to avoid growing resentment as you put in long hours and they don't.
Remember: you're probably competing with their day job for energy and attention. You know, the day job that feeds them and pays their mortgage. Those are strong forces to push against, so tread lightly.
Hire a contractor or employee and help them grow
If at all possible, pay your new partner something in cash in addition to equity. Even if it's well below market rate, it will motivate them to stay dedicated and alleviate the pain they feel from opportunity cost. It's easier to justify putting in that extra hour every night if you're seeing immediate returns from it — it's basic human nature.
Once the contractor has been working with you for awhile and you trust each other, simply start giving them more responsibility. Help them grow in to the technical cofounder role and compensate them accordingly.