Buy This, Not That
Never quit — get laid off.
Sam Dogen's Buy This, Not That applies named numerical rules — the 30/30/3 Home Buying Rule, the 1/10th Car Rule, and ROI-based education analysis — to transform major financial decisions from instinct into a binary, number-grounded verdict. The methodology covers seven life financial categories: housing, vehicles, education, career, relationships, investing, and retirement. Built on Dogen's 13-year Goldman Sachs career and his own early retirement at 34, the framework helps middle-income earners identify precisely which purchases build wealth and which quietly erode it.
“I'm looking at a $575,000 house. I make about $140,000 a year and I have $95,000 saved up. My lender just pre-approved me for $520,000.”
The 30/30/3 and 1/10th rules — a clear verdict on every major purchase you'll ever make
Buy This, Not That structures every major financial decision as a binary verdict — Buy This (the wealth-building choice) versus Not That (the wealth-eroding path) — applied consistently across seven life categories: housing, vehicles, education, career, relationships, investing, and retirement. The framework's anchors are two named numerical rules: the 30/30/3 Home Buying Rule (30% minimum down payment, monthly housing costs no more than 30% of gross income, purchase price no more than 3× annual gross income) and the 1/10th Rule for Car Buying (spend no more than 10% of annual gross income on any vehicle). These are supplemented by prescribed savings rate targets (20% minimum; 50%+ for FIRE aspirants), ROI-based education analysis that treats tuition as a business investment with a measurable salary-premium return, and Dogen's stealth wealth philosophy — accumulate aggressively, avoid lifestyle signaling, and prioritize real estate as the primary wealth-building vehicle for the middle class.
Most middle-income earners make their biggest financial decisions — buying a home, choosing a college, purchasing a car — based on what they can qualify for, not what builds wealth. A lender will approve a mortgage at 5× your income; a dealership will finance a $65,000 truck on a $55,000 salary. Without prescriptive numerical rules, you can do everything 'responsibly' by conventional standards and still undermine a decade of wealth-building potential in a single purchase decision.
Apply the 30/30/3 rule, the 1/10th rule, and ROI-based thinking to any major purchase and walk away with a specific dollar ceiling, a clear Buy This or Not That verdict, and a rationale grounded in Dogen's 13 years of investment banking and a decade of documented early-retirement experience.
- Your gross annual income (individual or household)
- The price or cost of the asset you're evaluating (home price, car sticker price, tuition total, etc.)
- Your current liquid savings and estimated savings rate
- The decision category: home purchase, vehicle, education, career move, or investment
- A Buy This or Not That verdict with the exact dollar ceiling the applicable rule prescribes
- A specific rule-violation report naming which of the three criteria fail (e.g., 'Your target is 4.1× your income — above the 3× ceiling')
- A stealth-wealth reallocation identifying consumption spending to redirect into compounding assets
- A FIRE savings rate timeline mapping your current percentage to a projected financial independence date
Watch the methodology work.
Three specimens from a single real session: the same situation, unaided and calibrated, the full transcript, and the skill answering live in the channel where the work happens.
“You're pre-approved for $520,000 and have found a $575,000 home you love. Your income is $140,000, you have $95,000 saved, and the monthly payment seems manageable. You've done everything right — consulted a lender, built savings, avoided buying at the absolute market peak. But something nags. You can't put a number on whether this is actually a smart move.”
“The 30/30/3 audit surfaces two failures: your target price is 4.1× your income (the ceiling is 3×, or $420,000), and your real down payment of $75,000 falls $97,500 short of the 30% required. Verdict: Not That — not because you can't afford the payments, but because this purchase violates the rules that separate wealth-building decisions from lifestyle ones. You now have a specific Buy This price range ($350K–$420K), an exact savings target ($105K–$126K down), and a 12–24 month runway to get there. The nagging feeling has a name, a number, and a plan.”
The same skill, where the work happens.
No new app to learn. The methodology runs over the WhatsApp Business API, so the answer lands as a reply in the thread you’re already in — same rigour, zero context-switch.
What it does, specifically.
Each capability is a distinct move drawn straight from the source methodology — not a generic assistant guessing.
30/30/3 Home Buying Audit
Input your gross income and target home price to receive a three-part audit: whether your down payment reaches 30%, whether your monthly payment stays within 30% of gross income, and whether the purchase price clears the 3× income ceiling. All three must pass for a Buy This verdict — a single failure means Not That, with specific numbers showing exactly how far you are from the threshold.
1/10th Vehicle Budget Check
Enter your gross annual income to receive your exact vehicle ceiling under the 1/10th rule, then test any specific car price against that ceiling. If the target vehicle fails, the skill identifies alternative tiers that fall within the rule and calculates the true annual cost of the overspend — including the compounding wealth destroyed by money tied up in a depreciating asset.
Education Degree ROI Analysis
Model a degree or school choice as a business investment: total cost (tuition plus four years of opportunity cost), expected starting salary premium above the no-degree alternative, and estimated time to recoup the full investment. The skill issues a Buy This verdict when the ROI clears the threshold and a Not That with a lower-cost alternative when it doesn't.
FIRE Savings Rate Mapping
Enter your gross annual income and annual savings to calculate your current savings rate, then map it against Dogen's prescribed thresholds: 20% minimum for baseline wealth-building, ramping to 50%+ for a meaningful FIRE timeline. The skill projects estimated financial independence dates at your current rate, your minimum target rate, and your aspirational FIRE rate — making the cost of under-saving visible in years, not percentages.
Stealth Wealth Spending Diagnosis
Review a snapshot of your monthly spending and identify which categories signal wealth without building it — visible lifestyle consumption — versus those that compound quietly into assets. The skill flags stealth-wealth opportunities: specific dollar amounts being spent on wealth-signaling consumption that could be reallocated without materially reducing quality of life.
Graded before it shipped.
Every skill is scored against independent scenarios for methodology fidelity before it goes live — not vibes, a rubric.
Buy/Not That Decision Scorecard
A verdict sheet for your specific purchase: the applicable rule (30/30/3, 1/10th, or education ROI), your numbers versus the prescribed threshold, a pass or fail on each criterion, and the exact dollar adjustment needed to convert a Not That into a Buy This.
30/30/3 Home Affordability Map
A three-axis breakdown of your home-buying constraints showing your maximum purchase price by the 3× rule, your maximum monthly payment by the 30% rule, and your current savings versus the required 30% down — simultaneously, so you can see where all three stand at once.
FIRE Savings Rate Timeline
A projection showing your estimated financial independence date at your current savings rate, your minimum Dogen target (20%), and your FIRE target (50%+) — converting abstract percentages into concrete years so the compounding cost of under-saving becomes tangible.
Stealth Wealth Reallocation Plan
A categorized breakdown of current spending split into wealth-building assets and lifestyle consumption, with specific monthly dollar amounts identified for reallocation — ranked by impact and friction so the easiest high-value shifts come first.
Grounded in the original work.
Every answer traces back to a real source and the practitioner who wrote it — not a secondhand summary. Here is the source of record.
Sam Dogen
Sam Dogen spent 13 years in investment banking at Goldman Sachs and Credit Suisse before negotiating a severance package and retiring at age 34 in 2012. He founded Financial Samurai in 2009 — one of the longest-running independent personal finance blogs in the United States — and published Buy This, Not That through Portfolio/Penguin in 2022. His own trajectory from banking analyst to early retiree is the proof-of-concept woven through every rule in the book.
Buy This, Not That: How to Spend Your Way to Wealth and Freedom (Portfolio/Penguin, 2022)
Former Goldman Sachs and Credit Suisse investment banker; retired at 34 via negotiated severance; founder of Financial Samurai (est. 2009); Portfolio/Penguin published author.
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