$400,000.00 Saved Up. I’m 24 And Am Looking For Passive Income. What Should I Look Into Thats Pretty Safe?

First, if you have any debts, pay them off.
Preventing a debt from growing counts the same as earning interest.
Second, I need a bit more info:
Do you have a specific goal and timeframe that you’ll be using the money? (retiring at age 50, or buying a half-million-dollar house next year)
Here’s my general advice:
Any money that you plan on spending within the next five years should NOT be put in the stock market.
It’s too wild a ride for the short term gains.
Remember the “day traders” ten years ago? 90% of them went broke.
Money markets are good enough. 3% interest is $12,000/year in passive, safe income.
For more than five years, a mix of mutual funds works.
As Warren Buffet likes to say “investing is boring”
Find four mutual funds with 10+ years, one from each category:
Growth, Growth & Income, Aggressive Growth, International.
You won’t find any with super high returns right now, because everyone got soaked last year. But it’ll come back.
Some people will suggest real estate. But there’s nothing passive about having to fix your tenants’ broken water heater, or keeping the crackheads off your property, or fixing a leaky roof.