Can I use Unity3d Free version as Indie developer while working in other companies?

Hello I am new to Unity3d. I really want to use it in my free time to create my own games and sell it.

Sure, you can. As long as you do not make more than $100k in one year. But if you work in a company which releases a game using unity pro, you will also have to have a pro version when working on that game.