My ultimate guide to boost my income. What works, what doesn't

Hi,
I live in London, and let me tell you something: it's INCREDIBLY expensive here! I guess it's the same for people who live in cities such as NYC, Paris or Tokyo. I work in advertising and make a decent income, and yet it's sometimes hard for me to pay the bills. So I had to think very hard to find new ways to make money.

It worked. But I also realised that lots of tips you find online to earn a side income are complete non-sense. I'm a bit mad at these marketing gurus who sell "Get rich quick" type courses that just don't work.

Here is what has worked for me so far, and what hasn't:

-Blogging and affiliation.
Definitely a great source of income if you know what you're doing, and in certain niches only. I'm a mum and write about travelling with kids, and this type of blog is a great way to earn a side income because you can contact big brands, let them publish sponsored posts on your website, become an affiliate, review their stuff for a fee etc.

-Renting your flat or parking space.
Renting your flat on Airbnb or your driveway/garage on YourParkingSpace is a very convenient way to earn a side income, especially if you live in a very popular, touristic city such as London or Brighton. These websites take care of everything for you, you just need to list your space for rent, and you earn money straight away. I think it's the easiest way to boost your income if you own something. Some people even rent their tools, garden or swimming pool!

-Self-publishing.
Another great way to boost your income, but of course, you must be a decent writer, and design (or get someone to design) beautiful Ebook covers to increase your sales. If you're an artistic person with lots of imagination, self-publishing books on the KDP Select platform is the best way to make money. The more you write and publish ebooks, the more sales you'll make.

-Etsy.
If you like sewing, painting, designing jewels etc, Etsy is another nice way to earn money. You need to be good with your hands, but the rewards can be incredible. I create jewels with sea shells myself, and they sell very well. But you have to market your creations on Facebook and twitter to make sales.

Now, what hasn't worked for me so far to boost my income...

-Merch by Amazon.
It's a service that helps you design t-shirts to sell them on Amazon. For the time being, I've had zero sales. Maybe my designs aren't good enough...

-Working as a freelancer.
I tried to work as a freelance translator on websites such as Upwork, but the businesses that contacted me were willing to pay me peanuts for the amount of work I had to accomplish. Maybe it's different for graphic/web designers or coders? I'm not sure, because I feel like there's more and more competition, and wages are decreasing at the same time.

Does anybody know other great ways to boost your income that I haven't covered, and that worked for you? :beer: