It depends on where you live. Many public places will require you to have a permit for sales. However, in a nice, family-friendly neighborhood as a kid, it would likely be fine. If you plan on selling street-crafts for a living, find out what the local regulations are and look into the costs of a stall, half shipping container or other form of suitable "pop-up shop" because you will be out there in all sorts of weather and you'll need to protect the crafts.
Start analyzing your decisions from the perspective of a firm. In economics, a firm's goal is simply to maximize profit. Well-run firms spend money only if they can expect to make more money from their investment, and they allocate their resources to the most profitable use. You're not a firm, of course, and you have other considerations, but if you make the majority of your time and money decisions by choosing the options that promise the highest return on investment, you'll likely earn more money, and that's good news for your shareholders (you and your family).
If you're not self-employed and work for a company, find out if they have a retirement plan. If you're lucky, employers will sometimes match contributions you make into a retirement fund. Retirement plans also often have the benefit of being tax-deferred. The longer you get to keep your money (and make interest on it) the better. It's never too early to start planning for retirement.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.
As for other tips, all I can say is “a penny saved is a penny earned”. If you are running out of ideas to make money, start saving. Some quick “low hanging fruit” tips to save some quick cash include – switch to MetroPCS or Boost for cellphone (I only pay $20/month), switch auto insurance to Insurance Panda ($25/month), and start using GasBuddy (saves me like $100/month at least. I drive a lot).
Selling clothes you no longer wear is a quick way to make some money. Start with local consignment shops for faster cash, or use sites like ThredUp and Poshmark to find buyers. If you go the online route, be sure to take clear, well-lit photos of your pieces and research similar items to set competitive prices. Get tips on how to sell your clothing.
If you’ve ever wanted to try real estate investing but don’t want to deal with all the stress of being a landlord, you might want to consider investing with Fundrise. Fundrise is a new platform that allows you to invest directly in a real estate portfolio that a team of professionals identifies, acquires, and manages on your behalf. With a starting investment as small as $500, you get exposure to dozens of solid, value-producing assets.