I think you need to think through what type of writing you would like to do and what market there is for that writing. You say you don't think you have a novel or even a short story in you- I don't either- which is why I don't write those. None of my journalist/writer friends make their money this way, most do copy-writing/editing/write non-fiction books. All would say, though, that taking on part-time and smaller contracts is not as lucrative as it used to be, there's a huge amount of competition from writing websites where contracts are posted, because lots of people can do this from home and so getting a stable and ongoing gig paying ok money is quite a difficult thing to do from scratch. AI is a competitor at the boring end of the marketplace (e.g, some website content).
If you want a full-time job that involves writing, then that's a bit different and I know people in publishing, commissioning, editing and copy-editing who do just fine, but I don't think that's what you are getting at- there's also comms jobs.
Working with English as a Foreign Language students on their dissertations or Masters/PhD thesis is another way to make money, as they often need help not only with the grammatical stuff but making it all make sense in another language, depends if you would find this interesting.
As for self-publishing, I wouldn't self-publish a novel but I would self-publish in other genres, if you want a small or even moderate income in a niche area of writing you know a lot about and others will pay for. Your memoirs, unless you are brilliant, less so.
Last- I agree with the person who said if you want to write, just get on with writing. The thought of writing, sitting alone and bashing out words, is appealing for people as a fantasy but the reality is that it can be lonely and a bit boring (if you don't love the subject matter) and the psychological struggle is real. If you want to write for money, start writing for free now- write anything you can, a blog, reviews, content for your friend's website, or try for that novel and see how it feels. Otherwise I'm not sure you will hit September and start writing; get some practice in now.