Probably a percentage of net profit based on the number of hours worked by each.
Talk to a tax professional about this. You have several choices of business entity, including sole proprietor. If you're a sole proprietor and your business partner is your employee, you'd report all the revenue on your tax return then deduct the payroll expense. If you form a partnership, you have guaranteed payments and distributive share (don't ask if you don't know - it's much too complicated for amateurs to pull off), if you're a corporation you could structure ownership any way you want and you could both be employees, if you're an LLC, you'd be taxed like a partnership unless you make an election to be treated as a different business entity. There are so many possibilities. Figure out in general how you want to split the profits, then talk to someone who knows what they're doing.
Business is not a DIY project. Don't try to navigate legal and tax issues unless one of you is a CPA or an attorney.