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Does this plan make any sense for early 20s investments?
I'm not following what's the meaning of "open a mutual fund". You don't open a mutual fund, you invest in it. There's a minimum required investment ($2000? Could be, some funds have lower limits, you don't have to go with the Fidelity one necessarily), but in general it has nothing to do with your Roth IRA account. You can invest in mutual funds with any trading account, not just Roth IRA (or any other specific kind). If you invest in ETF's  - you can invest in funds just as well (subject to the minimums set). As to the plan itself - buying and selling ETF's will cost you commission, ~2-3% of your investment. Over several months, you may get positive returns, and may get negative returns, but keep in mind that you start with the 2-3% loss on day 1. Within a short period of time, especially in the current economic climate (which is very unstable - just out of recession, election year, etc etc), I would think that keeping the cash in a savings account would be a better choice. While with ETF you don't have any guarantees other than -3%, then with savings accounts you can at least have a guaranteed return of ~1% APY (i.e.: won't earn much over the course of your internship, but you'll keep your money safe for your long term investment). For the long term - the fluctuations of month to month don't matter much, so investing now for the next 50 years - you shouldn't care about the stock market going 10% in April. So, keep your 1000 in savings account, and if you want to invest 5000 in your Roth IRA - invest it then. Assuming of course that you're completely positive about not needing this money in the next several decades.