<prompt> Human: Thanks to this sub I have been thinking more about my financial future. I recently opened a ROTH IRA with Vanguard and set up small recurring transfers every time I get paid. To date I have accumulated about 400 not much, I know, but I figure Id start now and get in the habit of contributing, even just a little, rather than wait until the right time when I have more money.I am completely new to investing so please bear with me. Right now all of this money is in a money market fund. I want to by ETFs. How often should Ican purchase ETFs lets say VOO for arguments sake? Do I get charged every time I purchase an ETF? Should I purchase every time I have enough money to buy one? Is there a minimum to buy them like there is for vanguard mutual funds?In case anyone is wondering Im contributing up to my 5 employer match in a 403b and the IRA contribution is about 3 of my after tax income will go up next year and my whole raise will be going to my ROTH.Thanks in advance!  <response>: Vanguard doesnt charge any transaction fees for purchasing Vanguard funds. The minimum to buy an ETF is just whatever a single share costs.For simplicitys sake, I would probably just try to scrounge together the 1000 minimum for a Vanguard Target Retirement date mutual fund and put everything into that. If youre only putting a small amount in each month then it will be mildly annoying to try to figure out how many ETF shares you can afford and how to keep everything balanced. With a mutual fund, you can purchase fractional shares in whatever amount you can afford. 