Hi,
hi did your son get an arranged employment from an employer in canada?it means the employer has applied and got a positive LMIA to support your son's pr under the federal skilled worker program,please note that the job offer MUST indicate the position is full time and indefinite once your son is granted pr.
what kind of clerical job is your son getting?because most of them are low skilled which means it will not qualify him to apply for a pr.
if its a semi or low skilled job and the employer gets a positive LMIA then your son can apply for a work permit but the job offer should be for a one period at a time because that is the duration a work permit can be issued for and not permanent.
please note that if he comes to canada as a TFW he can only extend his work permit for a limited period of time and his chances for pr with an unskilled positions are very low.