not all the business needs much investment - when COVID hit - many people started their side hustle from their home and they earned so much with zero investment
The side hustle needs dedication and that is the only thing which can make a business successful
There's affiliate marketing which is already known. You don't have to invest in stocks and products. The logic and simplest explanation of it is that you'll be promoting others' products and you need to use their affiliate link for you to have it count when someone clicks and buys the product you endorsed.
This is a side hustle but if you're able to make it your main niche and focus on the way of marketing it. You'll be able to earn a lot of passive income from it especially if you've made an interesting article/blog or video introducing the product and it gets viral.
Hmmm I think it is called PPC, I tried it last time and it is kinda hard for me since not all people will click your link. It is not like that one in the previous years, here in present they need to buy using your link, clicking your link can give you cents but it has maximum amount that you can earn by that. I earn something last pandemic when the market is slightly stable and many people wants my services but this year when bear market hits I lost all of them.