The most consistent returns I've ever seen people make is by flipping stuff.

What do you know a lot about? Cars, tractors, trailers, computers, cameras, antique furniture, whatever.

Buy the deals from dummies and desperates and resell.

My uncle has done this with tractors for decades. He might buy an 8n for $2,000. Clean it up, tune it, maybe a little paint. No more than a couple hundred bucks and a weekend of time. It'll bring $3,500.

He sells about 10 tractors a year.

And he dabbles in trailers too. People get to needing money and will sell things like trailers, ATVs, and boats at low prices. He doesn't make much off trailers, but it's quicker money than tractors. He'll make 2 or 3 hundred usually if he doesn't improve them any.