I try to work on my own cars instead of getting fucked by a mechanic, so if it's a job I haven't done before, I either try to look it up on YT, or ask someone who may have done that job.
One thing I've been thinking about doing is making furniture and stuff out of things like pallets, and selling them at farmers markets. Considering a lot of places are happy to have you take their pallets so they don't have to pay to get rid of them, you could make things for virtually nothing, save for the cost of your screws or nails, and sell them for a decent profit.
Just a thought I had about DIY shit.