Write that fact down on a piece of paper and both sign it. Then get it stamped by a public notary. Right now you're looking to make an agreement, not operate a

Write that fact down on a piece of paper and both sign it. Then get it stamped by a public notary. Right now you're looking to make an agreement, not operate a company. Most likely your only ownable asset for the foreseeable future is copyright, which you can agree to share equally with just a piece of paper - having a business entity won't actually help you unless you have either income or are ready to take on investors.