Built a free home affordability calculator based on take-home pay, not gross income — banks won't tell you the full picture

A friend of mine reached out recently stressed about the home purchasing process, constantly trying to figure out how much home they could comfortably afford. Not just what the bank approved them for based on DTI, but a conservative approach based on net income.

Gross income is a theoretical number. By the time it hits your bank account, several invisible costs have already been sliced off. Lenders have an incentive to tell you the maximum you can borrow, not necessarily what you can afford while still living comfortably.

They can't tell you what life costs on the other side of closing day. After taxes, car payments, student loans, groceries, and all the real-life stuff that never shows up on a mortgage application. Net-pay budgeting lets you bake in the real costs of homeownership: a $400 heating bill, a leaky roof, a water heater that doesn't ask permission before it dies.

The 50/30/20 rule takes it further. 50% of take-home for needs, 30% for wants, 20% for savings. It forces the home to fit into a balanced life rather than your life fitting around a house payment. The biggest danger of a large mortgage isn't the payment. It's what the payment quietly eliminates.

I went looking for a tool that showed the full picture in one place. I couldn't find one that did it well, so I built one. It's not perfect.

https://home-calculator-self.vercel.app

It's free. I'm not selling anything.

It calculates real take-home pay using actual federal and state tax brackets for all 50 states, your full monthly PITI, maps every debt and expense against your income, and shows affordability under three different methods. You can even model selling your current home and rolling that equity into the next purchase. At the end you download a full PDF report — one document you can actually sit down with.

A few honest caveats: this is not financial advice — please consult a licensed mortgage professional and tax advisor before making any decisions. Tax calculations are based on 2025 brackets and may not reflect 2026 changes, so treat those numbers as directional.

Would love feedback from this community — you'll catch things I missed.