Invest inside a Roth IRA. This is a tax advantaged account, where all the gains you make will be tax free when you take them out, after you hit retirement age. The money could grow 3 or 4 times, so that is a big deal. You can take out the money you put in tax free at any time. To do this, open a Roth IRA account at Fidelity.com. Deposit the $50 in that account. Then buy FSKAX or similar (the entire US stock market).