Business through employment

Depends whether that is not prohibited in your contract. IF there is no such condition for your employment then you can 

An employee has the right to start their own consultancy business as long as it doesn't interfere with their duties to their employer or breach any contractual obligations, such as non-compete or non-disclosure agreements.

Section 27 of the Indian Contract Act, 1872, states that agreements that restrain a person from carrying on a lawful profession, trade, or business are void. However, there are certain limitations. If the employee's consultancy business involves using confidential information or trade secrets obtained during their employment, it could constitute a breach of confidentiality obligations.

Additionally, if there's a non-compete clause in the employment contract restricting the employee from engaging in similar business activities, it might be enforceable to a reasonable extent. The case law of Niranjan Shankar Golikari vs. Century Spinning & Manufacturing Co. Ltd (AIR 1967 SC 1098) established that post-employment restrictions are valid if they protect the employer's interests and are reasonable in duration, geographical scope, and the nature of work restricted.

Efficiently managing one's time and prioritizing responsibilities are crucial for maintaining a harmonious work-life equilibrium. Anticipate the extra tasks and the disagreements that could occur.

You can - provided it does not violate the terms of emplyment and also, your performance and devotion to duty.

However, law apart, there could be unforeseen personal challenges.

You can start your company as long as your employment contract does not forbade you to do so. Employees in companies such as TCS, Infosys have explicit agreements in the employment contracts that says that you will not do any other work with any other business during the course of employment.