When do I register my sideline business?

From Entrepreneur.com.ph

In this edition of Ask The Expert, financial guru Henry Ong tells us more about business registration

Q: When a sideline business slowly becomes a “mainstream” business, when should I register with the DTI? 
A: When a sideline business starts to generate income higher than what you currently earn with promising prospects for expansion, you may consider registering this as a business. You have two options to register the business. You can register it as sole proprietorship under the Department of Trade and Industry or as a corporation with the Securities and Exchange Commission. Either mode, you should be ready with the following:

(1) Working Capital - How much do you need to sustain the business for the next six months? Are you going to finance it using internal earnings from the business? Or Are you going to borrow money from relatives or get investor partners?

(2) Manpower - Do you have the people with the right business skills to help you? Are you going to hire people from outside or invite relatives and friends to join you?

(3) Commitment - Are you going to give up your current job to devote your full time attention to this business? Or are you going to delegate it to someone you trust and run the business for you?