If you're looking to generate extra income, you may have more options than you think - even if you're already working full-time.
In David Pogue's upcoming 2016 book, "Pogue's Basics: Money," the Yahoo tech columnist provides tips and shortcuts to make money with little effort, on your own terms.
Here are six ways to line your pockets in your free time, including Pogue's estimates of how much you could make doing each.
1. Rent out your place on Airbnb
Particularly if you live in a tourist area or popular city, Airbnb can be a great source of supplemental income. In fact, Airbnb hosts in the most popular US cities make an average annual profit of more than US$20,000 (S$ 28,452).
"Next time you're away, don't think of your home as an empty building," Pogue writes. "Think of it as a giant piggy bank ready to be fed."
Of course, it is important to keep in mind that in some cities hosting guests through Airbnb is illegal, and in some apartments, it may break a contract.
Potential earnings: If you rent out your place two nights a week at $150 a night for 50 weeks a year, you can make $15,000 a year.
People will pay generously for someone to take care of their cats or dogs while they're out of town.
Pogue suggests using DogVacay.com, which is like Airbnb for pets: "You describe your setup, post photos of your home, and boast about how much you love dogs.
DogVacay lists you on its searchable site and provides insurance in case anything goes wrong."
Potential earnings: If you charge $40 a day for seven days, you can make $280 a week.
3. Sell handmade products on Etsy
Etsy is an online marketplace for jewelry, art, books, clothing, and more. Anyone can list their creations and sell them directly to millions of consumers all over the world.
"If you just set up your 'shop' and wait for the orders to flow in, you might be disappointed," Pogue notes. "The people who make good money on Etsy are those who have something fairly unusual to sell - and who put some effort into plugging their listings - on Twitter, Facebook, blogs, and so on."
Potential earnings: The average Etsy seller generates US$625 in sales a year.
4. Drive people around in your spare time
Driving for Uber or Lyft is a great, flexible side hustle, Pogue says: "As a part-time, whenever-you-feel-like-it sideline - for college students, parents at home during school hours, retirees, anyone who needs a little extra cash - the freedom of these jobs is unmatched."
The amount you can make depends on where you're located and when you're driving, he explains: "In big cities like New York, you can make US$25 an hour; in smaller cities, it's more like US$17."
Potential earnings: If you drive five hours day, five days a week, at US$20 an hour (minus 20 per cent to Uber and 10 per cent for gas and car insurance), you can make US$18,200 a year.
5. Do tasks or run small errands for people
You'd be surprised at what chores people would pay for you to do: Assemble IKEA furniture, pick up a package, pack your boxes, or proof-read documents.
"If you've got more time than money, you can sign up to help them, using TaskRabbit, a global marketplace for miscellaneous hyper-short-term labour," Pogue writes. "You list what kinds of work you're good at, you undergo a background check, you post your dollars-per-hour rate, and you wait for TaskRabbit to alert you of potential jobs nearby."
Potential earnings: If you work 15 hours a week, 48 weeks a year, making US$30 per hour after TaskRabbit fees, you can make US$21,600 a year.
6. Get paid to have an opinion
"Whenever you encounter a new product, movie, or ad campaign, well, you're not the first. All of them have been tried out beforehand on ordinary consumers. Specifically, they've been tried out on focus groups," Pogue says.
Participating in a focus groups generally involves giving feedback on a new product for a couple of hours. You get paid in cash, checks, gift cards, or prepaid Visa cards.
Pogue recommends checking out various sites: Focus Pointe Global, FocusForward, Brand Institute, Mindswarms, Toluna, and i-Say.
Potential earnings: If you do one focus group a month averaging $110 each, you can make $1,320 a year.