I wish you the best.
I would suggest you may identify the industry you would like to start your business. You can then attend the relevant courses in college . You can acquire better knowledge and understand how the industry works. You can also establish a good network with your classmates who will work in the industry in the future.
At the same time, you can analyze the status of industry works, e.g. any entry barrier, how's the competition, any substitute of the product, etc.
On the other hand, I would suggest you can seek opportunities to work in the industry. This can give you more visibility on the business process.
When you are ready to start, I would suggest you can consider to start it online (if it is feasible) given the startup cost is much lower.
Hope this helps! Good Luck!