Determining Pay for Security Guards
What you need to pay will depend on the general salary for security guards in your area. I am assuming that you are going to use an agency. In that case, they will tell you how much they charge. Ensure that minimum wages are paid. Also, ensure that the guards are not on 12-hour shifts but on 8-hour shifts and are given a weekly off, paid leave, and statutory dues are paid.
Night Shift Allowance
Giving a higher allowance for the night shift makes sense. However, today most companies do not do it because the guards are rotated every week or two weeks, and they all get to do night shifts. If you are paying for a higher night shift, that is a slightly more worker-friendly policy.