Then if it's a passion project it'll be important to remember that the rest of people won't be as passionate as you are and motivation will burn quite easily for them, especially for something long term that is unpaid.
Since it is your project, your passion, your story. What is there really for another individual, why would they collaborate in something that seems that benefits you more than them if not entirely only you? I'm genuinely asking because even good samaritans will end up being overwhelmed and frustrated in working on something that has no guarantee of being profitable, like, it's totally ok to feel confident.
But what if you don't make any income? What if your take several years publishing your series? How are you so sure you're going to be popular? How can you guarantee that the artist's efforts and time are going to be compensated?
Is ok to have a passion project and that making it is the greatest compensation for the passionate one, but for another... it is nothing but a task with no goal at the end of the road. So it is important to have some kind of compensation, be it offering your abilities as a writer for them to do something they want (Hence why you also need to share your portfolio), money or whatever that could interest the artist.
Of course, you can always draw it on your own even if it won't meet your own standards, there is literally nothing stopping you to try it out, ONE (One Punch Man and Mob Psycho) is a good example, same for the author of Ousama Ranking. Like any other artist, kid, hobbyist, etc, making comics is a good way to improve your drawing skills, especially if it's accompanied by a motivator like passion.