I am a master at side hustles so I have some ideas for you. I am not sure where you live but here is my current list - you do not need to do all these or any of them - I am just sharing with you to give you ideas how a small investment can pay off big time if you are willing to work at it.
Plowing snow - with a decent truck and a guy who likes to work I have made over 2,000 in one single storm. I was in the truck for 20 hours though. A cheap plow truck can be had for around 2,000 dollars.
Dump runs - If you have a truck for plowing snow you will also find a million and one uses for it in the summer. In addition to being helpful at Home Depot I use my truck to do dump runs for people. Often times it is trash and I just bring it to work the night before the dumpster gets emptied and load up our dumpster... on the flip side I have gotten some super high end pieces of furniture for my house this way. Nothing like getting paid to remove stuff and reusing it in your own house.
Mowing grass - this is one I am just embarking on - I have a commercial walk behind for my own property, a riding lawn tractor (actually 3), a push mower etc. So when Greg from my local meetup asked for someone to mow his property online I immediately volunteered.
Car flipping - I work at a garage and frequently find cars that need fixing. I will buy them and then resell them, occasionally I will do nothing other than wash it and take better photos. Other times there is more work involved. I like selling but hate working so I sometimes partner with a coworker - he is not opposed to doing work but hates dealing with people so it is a win-win for both of us. I also help friends and family sell just about anything and take a percentage or flat fee for selling there stuff.
Side work - As stated above I work at a garage - we always get our during the day work done first so at night I will work late and bring in a little bit of income helping friends and family with vehicle repairs.
Car detailing - this is pretty thankless and I am a perfectionist and you can't charge much for a detail and it takes me hours. I do not do things halfassed so it will probably take me an entire weekend to turn a car around.
Flea market flipping - my long time girlfriend has a fine arts degree - so she can refinish furniture in her sleep. I buy the stuff, she refinishes and relists it (she is also a photographer and good photos help sell. I see my initial investment back plus 20% of the profit.
Now you can flip anything - I have bought and sold cars, phones, guitars, tablets and the list goes on. Anything that is undervalued or poorly written and has bad photos is an easy pickup.
I keep a little bit of money in a Netspend savings account (5% interest on the first 1k in the account). This is use as my emergency fund or to store cash that I want to deploy quickly. It is safe and FDIC insured.
