Can I buy an ETF automatically every payday like I do with a 401(k)?

It's getting easier, but ETFs were historically harder to automate than mutual funds because they trade in whole or fractional shares at a live market price rather than a set end-of-day NAV. Many major brokers now support recurring, automatic ETF purchases including fractional shares, so you can invest a fixed dollar amount each payday. If your broker doesn't, a traditional index mutual fund is often the simpler choice for hands-off automatic investing, since you can buy exact dollar amounts on a schedule with no price-timing decisions. Check whether your broker charges anything for recurring buys (most large ones don't) and confirm it supports fractional shares. Automating contributions is one of the most reliable ways to build wealth, so pick whichever vehicle your broker automates cleanly.