how do you guys make alot of extra money?
I wouldn't say I make a /lot/ of extra money with my various side gigs, but they bring in a few grand a year, and some years more (reselling bitcoin mining hardware combined with mining on the hardware brought in around $20k extra, but that was a risky gamble at a specific point in time that's not reproducible - I bet heavy against Butterfly Labs on hardware that had other uses as well).
I have also thought about repairing things but cant think of what things would be worth repairing aside from laptops/electronics.
So repair laptops/electronics. There's good money available if you're
good at what you do, willing to work a soldering iron, and can tell someone with confidence that you can pull apart their very expensive laptop, repair what's broken, and be sure it will work out the other side. I'm employed at a big tech company with a lot of smart coworkers, and I'm one of very few people who takes on side repair work (laptops, tablets, phones... I'll touch almost anything). I've replaced fans, swapped screens, resoldered power jacks that melted out the center plug, replaced phone batteries (I actually keep Nexus 5 batteries in stock at my desk because there's such a demand for them - some of the phones apparently had a bad batch of batteries and they die in about a year), etc. It's not huge money, but it's certainly profitable (either in cash, or in whiskey - I will absolutely accept a nice bottle of Irish or Canadian whiskey for repair work). In the past, I also would buy broken laptops and either repair them or scrap them out. You can find piles of broken stuff on Craigslist from companies getting rid of stuff, and if you're willing to spend a few hours playing around and identifying what works and what doesn't, you can usually turn a large pile of broken hardware into a small pile of working hardware, a medium pile of tested parts (keyboards, screens, optical disk drives, power adapters, etc), and a small pile of stuff that's genuinely broken and is just scrap. Either use the working stuff yourself, or sell it, and then sell the parts. An older laptop is often literally worth more as parts than as a laptop (if you sell the screen, keyboard, top case assembly, lower plastics, mainboard, chassis, etc separately, you can frequently fetch way more than the laptop sells for). And be friends with your local pawn shops, since many of them like having places to get rid of broken laptops (though, sadly, this is common enough that you're not likely to turn much of a profit doing this anymore).
Oh, also, if you're confident in your abilities, car repair can be profitable. I fed myself for a semester of grad school on brake jobs for people.
Just get skills and go at it.
