Promissory notes remain valid for a duration of 3 years from the date of execution, after which they expire and become invalid. No maximum limit for which amount can be lent or borrowed.
There is not a federal usury law that sets limits on interest rates. There are state level usury laws, but they vary significantly by state. Also, the interest limits placed on a credit card issuer are determined by the state where they are based, not where a credit card holder lives.
Promissory notes with balloon payments are a financing option you may be considering for your business. These types of loans may be secured by collateral or not, but they always end their repayment schedule with a big payment, known as the balloon payment.