The only advantage to the flat monthly rate is that it is paid at the beginning of the month and then it is over and done and there is no chance through the month for the parents to negotiate a lesser rate if their child was away.

If you go with a monthly rate take a closer look at the calendar and figure out the average number of days and go from there if $800 is too low then add two days and charge $880 a month. Look at the full 52 weeks of the year to get your averages. Then months with 21 days pays the same as months with 23 days so it balances out. The monthly rate works fine if you choose the right monthly rate.

Personally I am paid weekly at a flat rate every monday.