If I loan money to a business, and they say they will double my investment in 4 months. Is that legal or illegal under the usury laws.It's in GA.

Is it a loan or an investment?  You say you loaned money to a business, but you also say that they promised to double your investment, so I'm not sure. If an investment, that means you buy an interest in the business and, if it goes up, the value of your investment goes up; if it goes down, the value of your investment goes down.  Generally, you can sell your stake at any time, although there can be restrictions on the right to transfer in some cases (either statutory or contractual.)  Usury laws don't apply to investments. If the transaction is a loan, that means that you have the right to be repaid in the agreed time period, and to receive the agreed interest (assuming it is at a lawful rate) and that's all.  You only get the interest on your loan regardless of how much the value of the business goes up (although your contract may provide for a "kicker" if the business does well, which would make the transaction somewhat of a hybrid between an investment and a loan), and conversely you get interest on your loan even if the business does poorly.  If your transaction was a loan, 300% annual interest would probably violate the usury laws (the allowable interest rate in NY is 16^ for a loan to an individual and 24% for a loan to a corporation; I don't know what it is in Georgia, but 300% per year seems way too high.)