Once you find a co-founder, what are the next steps you should take to start working together? In terms hours one can dedicate, responsibilities, project tracking, etc.
Agree with much of the prior responses.
Most important matter is clarity of YOUR REQUIREMENTS.
Many people are good at many things; whether they match up with your thinking, style, requirements, conflict management, aspirations, dedication etc is far more important. Until you've achieved clarity on those elements, the rest matters little. Culture and relationships will be built on trust in style, capabilities and in quality and quantity of purposeful execution.
If you've not yet done so, take an evening, and following 15 minutes of meditation (not medication) to clear your mind, get a pen and a few pads of post-it notes.
Start by listing 1 key element of fitness or requirement per note.
After you've identified your key elements, separate into your top 20, in descending order. Then, on each note, identify why it's important to a) you, b) the effort/product, c) the team you intend to build, d) your current or expected investors. Then clearly identify and articulate what exceptional performance looks like to you for each element, and to your other 3 audiences. Then determine a scoring system (1-5 or whatever your yardstick) of exceptional, over performing, par, needs help, needs to leave).
After you feel like you've dimensioned and prioritized that well, then develop questions and tools you'll use to evaluate candidates (lots of good ones exist). Until you do that, you run the risks of guessing, relying on feelings and hope, and hearing what you want to hear rather than the true facts and insights you need for your endeavor to succeed.
Your list will help you identify what the candidate needs to be great at to fill in where you're not strong. Doing this process will help you then collectively understand what you can and should outsource. It will give you, your product, your team (either now or as you hire them), and your investors the quality, clarity and confidence required to give you the best chance for success.
Brief, but-hope that helps. It may sound tedious, but the quality of thinking through those elements will deliver great dividends in helping you avoid mismatches, and in scoring and selecting the right person with the right skills and style for your endeavor and organization. It will also help for follow on hires, and in explaining your rationale to your team, your investors/advisers, and potential high profile clients.
The founders agreements is a document that co-founders can write up together (sometimes with a 3rd party mediating) that goes over responsibilities, commitments, who gets how much equity and a lot more technical details about the company you are creating. There are templates for these types of documents online, or one can go to a lawyer to help mediate.
It might feel uncomfortable to have to go over details such as what happens when a co-founder leaves, but these are conversations that are absolutely necessary before really beginning to work together. Without this framework, if you co-founder leaves, it could completely ruin your company.