Most people wait till they are close to retirement or when they have excess funds before they start thinking about starting a business. The following are the times I believe is best for anyone to start a business.
1. When you are young.
2.when you have no responsibility
3.when you don't find pleasure in working for others.
4.when you have an incurable obsession. Etc
Feel free to add yours.
Also start a business when you are in a community that lack basic needs such as water or electricity. You can start a water business and find ways to make a lot of money out of it. Basic needs are the things that the people can't do without and when you are able to solve such problems, they will keep buying from you daily.