I agree with pp that there’s no such thing as a ‘little business idea’
It’s really hard work to make money from a small business. You honestly have to love it and be really determined to make it work. It’s also going to take a lot more time than you think.
That’s not to say you shouldn’t do it. I think it’s one of the most rewarding things you can do. However, you need to be realistic about what it entails.
My advice (for what it’s worth) is find some time connecting with your interests and passions and see where that takes you.
If it’s just money you want, also agree with pp that a flexible/ casual job will give you more money per time spent, even at min wage.
Most of the reselling type businesses that have been recommended tend to take a lot of time for not much return.
A local cleaning, ironing, alterations service could work.
Longer term trying to connect with your interests again will point you to the right path, whether that’s retraining to do something or creating a business you really care about that.
A business you genuinely care about has a better chance of succeeding and not only giving you the money and lifestyle you want but giving you a personal sense of satisfaction doing something you find interesting.