How it works
Each rule answers a different question. The 30% rule and the landlord 40x test only look at gross income. The 28/36 rule also counts your debt payments. The 50/30/20 budget starts from take-home pay and leaves half of it for all needs, so rent has to share that half with essentials and minimum debt payments. In the example, $65,000 a year is $5,417 a month before tax: 30% is $1,625, and the 40x test allows the same $1,625. The 28/36 rule allows $1,517. But with $4,150 of take-home pay, $900 of other essentials and $350 of debt payments, a 50/30/20 budget leaves only $825 for rent. The gap between the gross-income rules and the budget is why a rent a landlord approves can still leave nothing to save. The monthly budget planner spreadsheet tracks the whole budget.