I'm not saying you'll fail. Please understand that.

That startup playbook that just came out, and countless other sources, anecdotes, etc all say the same thing : work with people you know, that you know well. Friends, former colleagues, etc.

It is quite a barrier to meet someone and jump on a project with them as a co-founder. Especially as a side project where the commitment level is low. I think you should think seriously on that.