The situation you describes is a partnership.
You and your friend will need to file a partnership tax return -- a Form 1065 . Each partner should show their pro-rata share of partnership income (reduced by any tax the partnership paid on the income), credits and deductions on Schedule K-1 (1065), Partner's Share of Income, Deductions, Credits, etc.
Let me know if you need any help.
You do not have to have a corporation to do any business or investment activities.
Based on your information - it looks as you entered into a partnership agreement with your friend
You do not need any registration to from a partnership - you may have verbal or written agreement with your friend and based on that agreement - file a partnership tax return.
Partnership is a separate entity and should file a separate tax return.
But partnership generally doesn't pay any tax - and all tax liability is passed through to partners.
If the check will be issued on your name and will be reported to the IRS as such - the IRS will expect that income to be reported on your personal tax return.
If that is not your income, - you might need to add a note to your tax return informing the IRS to prevent possible questions.
You will also report your share of the income.
partnership is the relationship existing between two or more persons who join to carry on a trade or business. Each person contributes money, property, labor or skill, and expects to share in the profits and losses of the business.
A partnership must file an annual information return to report the income, deductions, gains, losses, etc., from its operations, but it does not pay income tax. Instead, it "passes through" any profits or losses to its partners. Each partner includes his or her share of the partnership's income or loss on his or her tax return.
You may see more details in the IRS publication 541 - http://www.irs.gov/pub/irs-pdf/p541.pdf
As you are receiving an income reported on your SSN , but that income actually belongs to another person - you receive that income as a nominee.
Please see here how to report the income in such situations depending on different types of income - http://www.traderstatus.com/nominee.htm
Please provide that information to your tax preparer for considerations.