In my (unpopular) opinion, getting a raise is harder than getting a promotion. Think about it from your boss’s perspective, would you rather a) pay more money for the same service, or b) pay more money for additional responsibilities. Alas, if you feel you’re overdue a raise, check out Dr. Randall Hansen’s article on Getting the Raise You Deserve. There are some really useful strategies there.
If you have nothing of value to sell from home then retail arbitrage might be a better option for you. Many people partake in arbitrage to earn a little extra money, and for some it has even become their full-time job. Retail arbitrage is the buying of goods at a low price and then selling them on a different platform at a higher price. Sales in shops provide ideal opportunities to pick up products for next to nothing. These can then be sold on eBay or Amazon for higher amounts, making you a nice profit.
When creating a membership site, always offer different plans and pricing tiers to appeal to your different categories of audience. Access to specific types of content is then dependent on the plan selected by a member. Membership fees can be a one-off payment or a repeat subscription. And you can even sell products on your membership site to boost your income.
Drive for Uber or Lyft: If you're in a locale where you can find Uber or Lyft (or even one of the many competitors around the world such as China's Didi), you could easily make a respectable income. The hours are flexible and you can work as you see fit, making it perfect even if you currently have full-time employment but are looking to make some money on the side.
Whether you have a website or are still dreaming up ideas for a blog, you can also look into affiliate marketing. With affiliate marketing, you partner with brands and businesses within the content of your website. If you mention a product or service, you link to that produce or service using a unique affiliate code you received when you signed up for that particular affiliate program. From there, you’ll make money any time someone buys a product or service through your link.