Anything under minimum hourly wage is against the law even for live-in nanny or caregiver (domestic worker), so you probably have to be careful.  
You will also have to file for their EI and CPP and income tax and provide statement of earning with every pay cheque and T4 by the end of Feb.  
They are also entitled for paid public holidays, but you can deduct meal and board.  Below please find some information from HRSDC web site:
Ontario Prevailing Wage Rates and Room and Board Rates
G.T.A.                              $9.00 per hour 
Outside G.T.A.                      $8.00 per hour 
    
Hours of Work 30 to 48 hours per week 
Over 44 Hours per week Paid at time and a half 
    
Maximum Room and Board: 
                                    $85.25 per week               
                                    $369.42 per month 
Weekly Breaks Employers must give caregivers a minimum of 2 free rest periods each week consisting of: 
1 period of 36 hours in a row, and 
1 period of 12 hours in a row. 
 
Annual Vacation Employers must give caregivers: 
Vacation with pay after working with the same employer for 12 full months. 
A minimum of 2 weeks off work each year. 
Salary Deductions An employer must deduct and send the following on a regular basis to CCRA: 
Canada Pension Plan contributions 
Employment Insurance premiums 
Income Tax 
 
Room and Board An employer may deduct the following each week for room and board when the worker is paid minimum wage: 
For a private, locked room: $31.70 
For meals: $53.55
http://www.labour.gov.on.ca/english/es/factsheets/fs_domestics.html
In conclusion, 
5 days x 8 hours (9am-5pm) x $8 = $320 per week
$320 - $31.70 (board) - $53.55 (meal) = $234.75 per week
1 month will be $939, and that's the minimum you must pay "illegally".  Remember to calculate the CPP, EI, Income Tax etc, WSIB..