Letâs look at a hypothetical spontaneous chemical reaction: The quantity of usable energy (chemical potential) in a reaction is called the Gibbs Free Energy (DG). DG is the difference between the energy contained in the products of a reaction and the reactants: DG = (energy of products) - (energy of reactants)
That's why some financial experts feel it's more realistic to think in terms of your net income, aka take-home pay, and that you shouldn't use any more than 25% of your take-home on your mortgage payment.
One weekâs paycheck is about 23 percent of your monthly (after-tax) income. If I had to set a rule, it would be this: Aim to keep your mortgage payment at or below 25 percent of your pretax monthly income. Aim to keep your total debt payments at or below 33 percent of your pretax monthly income.