Compulsary features for a wordpress theme?


Hello Authors,
Its a nice tag #author #developer

I am new on Envato, Want to know compulsory fetaures which should be included in my theme.
I want to create everything from my hand, I cannot buy extended plugins and use them in my theme.
So kindly guide me in how many month, I can complete a theme (multipurpose) which can make me millionaire.