If your prospective employer is offering you work without deducting any taxes, then I would strongly urge you to look for another job.
By doing this, the employer is most likely trying to pay you below minimum wage and thus would not provide you with a work contract. Thus, you will have no protections or compensations available to formal workers (such as being injured on the job). Also, if he refuses to pay you at the end of the year or pays you a lesser amount - you will have no legal recourse.
As an International student, you are allowed to work a maximum of 20 hours per week. Assuming you'll eventually apply for a PGWP or PR, its probably best to have all your dealings above board and be on the right side of the law.