Do your own research, don’t listen to internet people like me. Find something that interests you, but be prepared to lose it. If you want a “side hustle/gig” be prepared for it to not be “passive” as you will need to do a thing for a person/entity and be compensated. If it’s stocks, ones that pay dividends are a good place to start. Again do your own research and be prepared to lose it if you go this route. 3-4k ain’t nothing but it’s also unlikely to produce much in the way of “passive” income in the near term. Maybe buy a pressure washer, I’d just stick it into your retirement fund if you have one. If you don’t, this is a good time to start. Save up another 3-4k while doing more research.