I'm new here and trying to understand the 50% rule

[Account Closed]

For example: i wanted to know if I had rent coming in at $1000 and mortgage is $400, which the rule states that 50% of the income will go to expenses and the other will pay for the mortgage and the reminder will be the cash flow. So I'll put $500 in the expenses column and the other $500 I'll use to pay $400 for mortgage and then keep $100 in my pocket. But what if for a whole the unit or home doesn't need any fixing just painting will I still keep that $500 in the expense column or I then put it in the cash flow column since I don't have to use it?