Let's face it, there's a lot of writers out there looking for artists. In fact, if you tell most artists with a comic that you want an artist, they'll tell you "yeah, me too"
And there's a good reason for this! As somebody who solved the artist problem by learning to draw myself, my writing takes about half an hour a page, while the art takes up to eight hours a page. That's a lot to ask somebody to put into your idea! Especially when there's a good chance they have their own stories to come true.
Being willing to pay (and pay upfront. paying in potential profits is asking them to take a part time job that may or may not pay) is always going to be the best way, but I know plenty of you have a passion for comics, but can't draw or pay, so here's my advice:
Have Reasonable Expectations
Most professional comic pages in America have three artists (inker, penciler, colorist), each of whom is making ~40-100 bucks. Japanese writers not only often draw themselves, but usually have extensive art teams helping with all the details. You're looking for one person to do all those jobs for free, which means you aren't going to get a comic that looks like the ones you read.
On the other hand, there's tons of beginners looking for projects who would love to help make your idea come to life. If you go in knowing that, even with years of practice, you're a beginning writer, you can build a team that will help both of your careers grow.
Build a Following
One of the biggest things that draws an artist to work on a project is passion, which means you have to get people passionate for your work. I mean, look at all the writers on Tapas who started as popular novelists and went on to find artists. If your writing is good and marketable, then you should be able to get people excited for it even without art.
See if you can get published in a short story journal, post a novel, get onto the fanfic scene, whatever gets hype. If you can pay a bit, but not for a long term project, consider writing a short story as a portfolio piece. Most writers who get professional gigs without a writing history came from popularity from another project or medium.
Show Your Story (and Your Skill)
Even if you don't have a following, you can still get people excited, and that is by showing them some dang good writing. A brief plot summary can help get artists interested, but you also need to flaunt your actual skill.
While artists can post an image to show their skill, showing good writing is harder. I think the best thing you can do is link to the script you want illustrated. This shows your writing, the project, and how clearly you communicate your ideas to an artist (and understand what fits on a panel and a page). It's also good to put it through the edit wringer beforehand.
Respect Their Work
Again, you're looking for free work on your project. Don't feel insulted if artists will only work for pay or aren't into your idea. It's part of the process, and it's not an insult to you, or artists being unfair. I think what frustrates me the most is getting frustrated that artists are drawing their stupid story over your good story. Every comic is a work of love, and they probably love their story and don't find it stupid. And they might be somebody who's worked hard and loves writing making their dream come true. Calling people's hard work stupid isn't the way to make them want to work for you.
Help Where You Can
Again, the biggest barrier for artists is time, so if you can lessen that time, you're waaay more likely to draw in artists.
This isn't because writing is less good or important than art, just that in time per week, artists tend to need a lot more help. You probably can't do the actual drawing, but your artist might really love help with the flat colors, dialogue bubbles, and formatting for post.
You can also show off non writing skills you bring to the table. If you're a marketing whiz, a potential artist might really appreciate it.
Good luck getting your story out there!