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.
That's $3600/year together, or $300/month. So your total monthly mortgage payment is $1320 ($1020 from what we figured earlier, plus $300 for taxes and insurance.). One more thing: If you put less than 20% down, you'll probably have to pay for Private Mortgage Insurance (PMI).hat's $3600/year together, or $300/month. So your total monthly mortgage payment is $1320 ($1020 from what we figured earlier, plus $300 for taxes and insurance.). One more thing: If you put less than 20% down, you'll probably have to pay for Private Mortgage Insurance (PMI).