BlindAssasin you're kidding right?!
"Presumably he pays rent/bills/food/entertainment for OP... Now the kids are at school and childcare is minimum hours he could pay someone about £400 a month to do this work... I bet OP costs him more than that!"
Ok lets be generous here. Say OP works 9-5 4 days per weeks, allow 45 mins to get out door of work to door of CM who charges 3.5 per hour per child, factor in drop off times etc so on a school day OP is paying for 16 hrs worth of care. Which = 224 per week.
Most schools have at least 15 weeks holiday a year so that is 15 weeks of full day care for four children. 560 per week. Say mum and dad take their hols seperately and subtract 6 weeks of that total = 5040
Total childcare bill before ill children/snow days any other drama factored in etc = 13,328 or 1,110 per month.
Which means you have to be earning about 17k just to break even.
Now if you can show me a job that pays that money for working 9-5, four days a week, with limited commute where OP would have no work related expenses (bus parking petrol) in an area where childcare is only 3.5 an hour you might have a point but it seems unlikley.
This of course ignores the fact that all the OP's domestic duties would also have a value and most significantly who the hell wants to work in a job (not a career) just to break even - or in fact make a loss as soon as one of the kids is sick?