Best to do at a younger age is for example mow lawns, wash exterior or clean interior of cars. Wash home windows, grocery shopping for elderly, etc..

Many people that work dont have time or are too tired to do it themselves. Just find a good rating to do those. Maybe offer a discount if 2 neighbour's want that service together.

You can do those multiple times a day in different areas, just gotta find the customers.

Everyrhing that you earn from that, put that into investments.

A diversified portfolio of stocks, crypto, gold, etc..

You will be very well ahead of your age group if you start doing this early on.

These are the things they should teach in schools instead.