There are quite a number of sites that allow small writers to make money without huge expenses and Kindle is one of them. I learnt about writing on Kindle a few years back, but I didn't do it because it seemed to be tasking.
One major challenge I learnt of was choosing a niche to write on that people like. If you don't have the skills, or the patience to learn gradually till you get it right, you won't make money on Amazon Kindle Publishing.
You might also need to promote your books, which means you need money for the ads. Not everyone has money to spend on the ads.
Wattpad seems like a better option, with less competition and lower standards. The pay is more on Kindle though and it's easier to get better results back with less effort.
The best thing to do if you want to become a writer on Kindle is to get a mentor to guide you to success.