Running a business of your own is an activity you can tailor to your available times and resources, perhaps starting with very little. If it matches your own Risk Profile, then start with a small sum of money and do what you can to increase the fund.
Beyond the Compound Interest way of investing your money, look at the simple concept that you invest a basic sum and double it - gaining yourself a 100% return.
The best way to do this is always through learning to Sell Something.
Selling is the simplest of skills to learn at a basic level and you can choose later to get really good at it.
Start by finding something that you like enough to carry with you all the time. When someone expresses interest in it, you say,
"It's for sale. Would you like to buy it?"
I am sure that the reason most people express a fear of selling, is because they can't be comfortable waiting for the silence to be broken after asking this question.
If the person says "Yes", then you have a sale. And you might have doubled your investment.
Do the research and see what you can invest in, for the short-term, the medium or the long term. Again I would recommend that you assess your approach to risk and always work within the boundaries of what is right for you.
The development of a good set of selling skills is a prerequisite to success not just in business but in a lot of personal and social situations too, and as such should not be overlooked as a skill worth acquiring.
Face to face selling can be done at a street food stall if you can cook well. You could buy a collection of household items and sell them at a weekend car boot event. If dealing with the public face to face does not appeal then instead focus on selling via one of the online outlets such as Easy, Ebay or Amazon. You can be up and running within an hour, even after taking pictures of your starting stock. You list the items for a fixed price or for an auction style sale and you then wait to see how your offering is received. The process is simple and your costs are predictable based on the published percentage charge that the web platform applies.
If you want to make things at home and sell them online there are a mass of specific sites where the audience comes and searches for home made, craft or vintage items. Do your research and look around for a selling activity and opportunity you can feel comfortable with. Start simple and set yourself a budget for the first batch of items you will collect or make yourself and list these for sale.