An immigration lawyer will charge you anywhere between $2k-5k at the minimum to be your representative. You will have to find one and talk to them directly to learn about their fees.
99% of the applicants do not use an immigration lawyer to apply for a study permit and instead start here:
http://www.cic.gc.ca/english/information/applications/student.asp
Also,there is no such program as "work on study" in Canada and the duration of study permit will depend on the length of study. If you are granted a study permit, you "may" be eligible to work 20 hrs a week off campus, unlimited hrs on campus and full time during breaks.
You can submit this form and see if you can find out the actual cost of being represented by an immigration law firm to obtain a study permit:
https://www.canadavisa.com/contact-us.html
Good luck.