Regarding the minhag of mayser ksafim, does it go by total monthly profit? For instance,if I have to pay gas-electric bills, rent, food babysitters, gas for my car etc, is all that taken off my work profit before I calculate? I know I recently asked a similar question but wanted to clarify the exact number.
Only work-related expenses can be deducted from the maaser calculation. Therefore, if you need the babysitter to allow you to go to work, this expense is deducted. The same is true for gas to go to work, for the rent of the office,and so on. However, the tax you pay on the car is not deducted, because this is not a work expense, but an expense you would pay irrespective of work.