Laure Boi,

          First of all my suggestion for you will be finish your study and start you own professional carrer.

          However, If you are alredy maked your mind to start a business then, you can invest in the bussiness like in a partnership. But, you cannot take the ownership. I mean that the business cannot be run under your name in any topics. other sharing the profits or stuff can be done by creating a mutual understanding between the partners.