Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Personal Loan issuer online service
Here is a simple loan payment calculator.  If you allow early principal repayment, then you should just be able to plug in the new principal amount to find his new monthly payment (someone please correct me if I'm mistaken). Are you averse to creating a spreadsheet yourself in excel?  I suppose it could become quite an undertaking, depending on how detailed you chose to get with the interest.  Seems like it would be more direct and serve the dual purpose of recordkeeping. It's important to agree in advance whether pre-payments go to principal or go partly to interest (prepaying for periodic amounts not yet due, which are mixed principal and interest).  It's a family loan, so it probably makes sense to allow the prepayments to pay down principal; you don't need to structure your interest income and prevent him from depriving you of interest income (which many bank loans will do).  Allowing early principal repayment is pretty easy to calculate in your own excel spreadsheet, since you just need to know the remaining principal, time outstanding, and the interest rate. Note that if you are a US citizen, then the interest paid to you will be taxable income to you ("ordinary income" rate).  Your brother will not be able to deduct the interest payments, unless maybe they are used for something like his business or perhaps mortgage.  There is no deduction for just a personal loan. Also, if you instead structured it without interest, then the interest not charged would be considered a gift under US gift tax law.  As long as the annual interest were under the gift exclusion amount ($14,000) then there would be no gift tax.  With no interest and no gift, you would not have tax consequences.