Money & credit

One amortization schedule sits behind all of these. What changes is the question asked of it — what the payment is, what it costs over the full term, what an extra hundred a month saves, or when refinancing pays for itself.

• 15 vs 30 year What the shorter term costs each month, and what it saves over the loan.
• Amortization schedule Where each payment goes, year by year, and how slowly the balance actually falls.
• Biweekly payments What paying half the mortgage every fortnight actually saves, and why.
• Closing costs What you actually need on the day, beyond the deposit.
• Extra payment What paying a bit more each month saves in interest, and how many years it cuts.
• Line of credit The interest-only payment, and what it becomes when the draw period ends.
• Home equity What share of the house is yours, and what a lender would advance against it.
• Affordability What a monthly payment you can manage translates into as a purchase price.
• Mortgage payment Monthly payment, total interest and what the first payment actually pays off.
• Discount points Whether buying down the rate pays back, and in what month.
• Mortgage insurance What mortgage insurance costs, and when you can get rid of it.
• Refinance break-even How long the lower payment takes to pay back what the refinance costs.

Every one of these is the same amortization maths as a mortgage, over a shorter term and usually at a higher rate. The rate is always yours to enter.

• Car affordability What a monthly budget buys once insurance, fuel and upkeep come out of it.
• Car loan Monthly payment and total interest on car finance, at your own rate.
• Lease vs buy Both payments side by side, with the car you own at the end counted properly.
• Personal loan The payment, and the rate you are really paying once the fee comes out.
• Student loan The payment, and what the interest accruing before repayment adds to it.
• Student refinance What a lower rate saves, and what refinancing federal debt gives up.

Two strategies dominate: clear the smallest balance first for the momentum, or the highest rate first for the money. These show what each actually costs, so the trade-off is a number rather than an argument.

• Credit card payoff How long a balance takes to clear, and what paying only the minimum costs instead.
• Debt consolidation Whether one loan really costs less than the debts it replaces.
• Debt payoff plan Which debt to attack first, and what each order costs you.
• Minimum payment What paying only the minimum costs, and what simply not lowering it saves.

Compounding is the whole subject. These show what regular contributions become over time, and what reaching a target actually requires each month.

• CAGR The annual rate that turns a starting value into an ending one.
• Compound interest What a balance grows to, and how much of it is growth rather than deposits.
• Savings goal What you need to put away each month to reach a target by a date.

Everything here rests on two numbers you supply and nobody can promise: the return and the time. Time is the one that does the work. A pound invested for thirty years has to grow at a modest rate to become several; a pound invested for five has to grow at an implausible one.

• Retirement account What a workplace account grows to, with the employer match counted properly.
• Direct vs regular funds What the distributor commission inside a regular plan costs you over the years.
• Financial independence How long until the portfolio covers the spending, at your saving rate.
• Roth vs traditional Pay the tax now or later — and why the answer is just one comparison.
• Regular investing What investing a fixed amount every month grows to, with an annual step-up.