There are a lot of different options here, and which one is best depends on a great many things.  You should talk to a lawyer about this, and one place to look for an attorney who can explain your options and set up the necessary paperwork is our website, http://attorneypages.comThe simplest way to do this is a promissory note, an i.o.u., that would have the interest rate and repayment terms.  Your investor would not get a piece of the business, he would be a creditor.  There are a number of different ways to set that up.  And the investor might not be satisfied with that.You could also make the investor the eighth partner, and you would probably want a written partnership agreement that describes each partner's share of the business.  A variation on that is a limited partnership, in which one or more partners does not get to run the business on a day-to-day basis, but gets a share of the profits.Other alternatives are forming a corporation or a limited liability company (LLC).  Each of these possibilities has its own advantages and disadvantages.Your lawyer will want a fair amount of information, to help you choose -- and to negotiate with your investor and his lawyer.  There are different tax consequences, sometimes, and your lawyer will probably want to talk to your accountant as well.