Acorns tries to overcome the savings and investing hurdles millennials face. Once linked to your credit or debit card or PayPal account, Acorns rounds up purchases to the nearest dollar and invests the difference in one of fie diversified exchange-traded fund portfolios. You can also set up automatic investments from your bank account. The Found Money feature earns cash back at participating companies like Airbnb and Macy’s. Fees start at $1 per month, which sounds minimal, but for small investors, these “fees could be comparatively large,” warns Jackie Shroyer, a senior analyst at Corporate Insight, adding that Acorns waives all fees for students with valid .edu email addresses.