Use-cases hub
Real-World Money Decisions — Solved
Every use-case answers a specific question a professional, freelancer, or business owner actually asks. The math behind the answer. The calculator to run your numbers. 20 worked money decisions covering retirement, tax, housing, debt, business, and equity comp.
20 real-world money decisions
Specific answers to specific questions
Each use-case takes a common financial question — “How much do I need to retire at 50?” “Should I refinance?” — and walks through the answer with the right calculator. Every figure is arithmetic from assumptions the page lists, so you can change them.
01 · Retirement
Retiring at 50: How Much Do You Need?
35-year retirement window with sequence-of-returns risk.
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02 · Retirement
Retirement Nest Egg for $50K Annual Expenses
The 4% rule applied to your actual lifestyle.
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03 · Retirement
$400K Lump Sum or $2,100 a Month for Life?
A 6.3% implied payout against a 4% withdrawal — and what each protects you from.
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04 · Retirement
Student Loans at 6.5% or the 401(k) Match?
A 50% instant return no loan rate competes with. Take the match first.
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05 · Retirement
Roth Conversion at 60 — Worth the Tax?
Partial conversions in low-income gap years.
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06 · Retirement
Backdoor Roth IRA on $250K Salary
Four steps to bypass the Roth income cap legally.
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07 · Retirement
Mega Backdoor Roth for Tech Employees
Route after-tax 401(k) contributions into a Roth.
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08 · Housing
How Much House Can I Afford on $120K?
The 28/36 rule worked properly — and why the back-end ratio usually binds first.
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09 · Housing
Monthly Payment on a $300K Mortgage
Principal, interest, PMI — the full picture by rate and term.
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10 · Housing
Should I Refinance My 5% to 6% Mortgage?
When the math says no — and the right break-even formula.
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11 · Debt
$15,000 on a Card at 24% APR
The minimum takes 28.7 years and $28,887. A fixed $500 takes 47 months.
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12 · Debt
Pay Off the Car Loan Early or Invest?
$1,930 guaranteed against $3,624 expected — closer than the rates suggest.
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13 · Saving
How Big Should My Emergency Fund Be?
Three, six or nine months — what each costs and how long it takes to build.
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14 · Saving
Funding a $60K College Bill in 10 Years
$366 a month reaches $60,000. Education inflation is why that is the wrong target.
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15 · Tax
Quarterly Tax on $200K 1099 Income
Safe-harbor rule and the set-aside framework that avoids the penalty.
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16 · Tax
HSA Triple-Tax Strategy
Deductible in, tax-free growth, tax-free out for medical costs.
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17 · Equity
RSUs Just Vested — Sell Now or Hold?
Already taxed as income. Holding is a fresh decision to buy your employer.
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18 · Business
S-Corp Salary vs Distribution
Splitting profit between wages and distributions, and where the line sits.
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19 · Business
What Hourly Rate Replaces a $95K Salary?
$45.67 is the naive answer. $84 is the one that actually replaces it.
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20 · Business
ROI on a $10K Marketing Campaign
CAC, payback, LTV — the unit economics test.
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