I'll throw a different one in the ring since everyone's covering VA/Canva work: iGaming (casino/sportsbook) affiliate. It's been my main income for 10+ years, so speaking from experience, not theory.
The honest version - it's not a "no experience, earn today" thing, so don't let anyone sell you that. But it's one of the highest-paying affiliate verticals there is (revshare on a player can pay for months, sometimes years), and the skill you build along the way - SEO, content, understanding search intent - transfers everywhere.
If you want to test the water without money upfront: pick one narrow angle - one game, one country, one payment method people search for - and write genuinely useful content around it. Real reviews, real detail, stuff AI can't just spit out. You learn SEO and content as you go, which is the actual asset.
Two things to respect from day one: only promote in markets where it's legal and licensed, and always run the responsible-gambling messaging. Cutting corners there is what gets sites and affiliate accounts killed. Do it clean and it compounds.
Happy to point you at how the payout models (CPA vs revshare vs hybrid) actually work if you want to go deeper.