It depends on your financial status, the type of business you will be operating, the work you are willing to put into it, and how long you are willing to wait for results. Can you build this business with your current finances, or do you need to take out a loan?
We would need more information to give you better advice.
For example, if you are going into a line of business that competes against others that are going out of business, you would face a small available market right now. But when the economy begins to come back, you would be in a very good position to take a larger portion of the regrowing marking.