One more tidbit: There are always ETF’s (exchange traded funds). The minimum to buy is one share (varies). They’re bought through brokerage accounts. Individual brokers (Schwab, Fidelity, E-Trade, Vanguard, TD, etc.) have their own groups of ETFs with no brokerage commission. If you buy them through Robinhood, all ETFs that you’re able to buy there should have no commission.

There are also plenty of low-cost stock and bond index funds you can buy at Schwab. Some of these Schwab Funds have investment minimums at $1. Maybe worth a look at. I do own some.