In looking for a second income, look for opportunities within your field first. If you are a painter, or lawn care provider, a handy man job is an extra chance for extra dollars. A weekly lawn care provider must charge extra for taking out plants and replanting a decorative plot. If a service was not included in an original agreement, you must be paid for extra work.
Painters have a skill that is usually included in the price of a house painting job. A painter pressure washes a building before painting it. You could advertise a power wash as a means to preserve the paint job on a house. Roofs need power washing. Trees rain down leaves and pollen that rot on a roof discoloring it or damaging it. A painter could advertise power washing a roof to add visual value to a home and preserve the investment. Painters also repair cracks and damaged pieces of wood. Advertising or offering these extra skills to make extra money. Some of these same skills are possessed by roofers, handymen and general laborers.
A homemade computer printed business card is a good way to start advertising, as well as this site that offers free business cards.
For those who think they have no skill, let me tell you something. I used to work in a factory organizing and assembling small electronic parts. I take instruction well. My job now is as it was then, all about the little details.
If you are general office help, not working a full week, type Temporary Professional Service in your search engine. Take on one or two days a week as a temp. If you let yourself shine, you may be offered a better job than the one you have, I was. What about those moms you know who have to work weekends to keep their jobs? Why aren't you babysitting their children?
I know a nurse who works her two twelve hour shifts on her two days on and two days off schedule, then she watches the two children of her nurse friend for six hours a day till her husband picks them up. It works for both of them and gets her some extra money while her friend doesn't worry about her children for her two days. I also know a woman who was complaining about the school her children attended and a teacher whop was cut back out of her job. I put the two of them in touch and now the children are home schooled with a proper tutor who is making more than she made in public school as the mom is paying less than a private school. You can use your skills to make money,too.
If you are still convinced you have no marketable skills or you are tied to the home for one reason or another, clean your closet, your garage and the kids old clothes and toys and have a yard sale. Babysit for one or two on a week end night or a Tuesday mom's day out. Then, when you have some confidence, offer to do the same for a neighbor.
After my grandmother retired, she made more money babysitting three days a week for five hours than she made working a forty hour week. She did two Mom's day out jobs and a Friday night out. She was booked every week for over a decade. The only time she wasn't booked was for her own holidays and vacations.
Maybe kids and home skills are not your forte. Raise a rare breed of small animal within the legal guidelines of your state or community. My sister has a gift with small animals and almost cornered the market on fancy finches in pairs. I know a lot of people who used to or still....one guy sells fancy guppies he raises in three 50 gallon tanks in his home. It's a hobby that pays for itself and some extra....A lady who scans up people family photo albums. She doesn't 'fix' the pics, she just scans them and gives them back with a thumb drive of photos....
For those with actual training (military) maybe you could advertise personal camping skill training or get involved in the local woodland hiking crowd and offer training for surviving a fall or being lost. My former Marine goes to the state funded gun range from time to time. Our hunting licenses pay for it, so we go. EVERY time he goes, he ends up with someone asking for some training or asking how he made his target stands, or where he got the range is hot red flag. (His mom taught him to sew) He never fires without raising a warning flag. Neither should you and he takes along an extra for anyone who offers to purchase one of their own.
Maybe you have over purchased a few first aid items. You could assemble your own first aid kit and sell them at your yard sale, then a flea market if you want to go in to business for yourself.
You may be a survivor entrepreneur waiting to happen. You may be the new yard sale queen or the new clean roof king. Whatever you find that is right for you, look for that second income inside of you and invest it in your future survival.