Sources

S1 — Wikipedia: Compound interest

authority: encyclopedia
supports: Lesson 04 — the definition of compound interest, its contrast with simple interest, the periodic-compounding formula, and why compounding frequency changes the result.
key-fact: "Compound interest is interest accumulated from a principal sum and previously accumulated interest." It "is contrasted with simple interest, where previously accumulated interest is not added to the principal amount of the current period." The periodic formula is A = P(1 + r/n)^(tn), where P is the principal, r the nominal annual rate, n the number of compounding periods per year, and t the time in years; "the compounding frequency is the number of times per given unit of time the accumulated interest is capitalized."

authority: official-docs
supports: Lessons 04 and 06 — a free official tool to project how a starting balance plus a fixed monthly contribution grows, with a selectable compound frequency; used for the terminal one-page plan.
key-fact: The SEC's calculator takes an initial investment, a monthly contribution ("Amount that you plan to add to the principal every month"), a length of time in years, an estimated annual interest rate, and a compound frequency (Annually, Semiannually, Quarterly, Monthly, or Daily — "Times per year that interest will be compounded"), and shows "how much your money can grow using the power of compound interest."

authority: encyclopedia
supports: Lessons 01 and 02 — a budget as a plan coordinating income and expenses, the 50/30/20 split on net income, and the zero-based idea of allocating every unit of income before spending.
key-fact: A personal budget is "a plan for the coordination of income and expenses." Under the 50/30/20 method, "50% of one's net income then goes towards needs, 30% towards wants, and 20% towards savings." Under zero-based budgeting, "all of one's net income must be allocated ahead of spending" so that "at the end of the month there is a zero balance in the budget."

authority: encyclopedia
supports: Lesson 03 — the definition of an emergency fund and the kinds of unplanned expenses it exists to absorb.
key-fact: "An emergency fund, also known as a contingency fund, is a personal budget set aside as a financial safety net for future mishaps or unexpected expenses." It is used for events such as "job loss, medical emergencies, automobile problems, home appliance repairs and replacements, and unplanned travel expenses."

authority: official-docs
supports: Lesson 03 — that an emergency fund is a cash reserve for unplanned expenses, that even a small amount helps, and that it belongs in a safe, accessible place.
key-fact: "An emergency fund is a cash reserve that's specifically set aside for unplanned expenses or financial emergencies." The amount "depends on your situation," but "even a small amount can provide some financial security," and the guide recommends keeping it somewhere safe and reachable such as a bank or credit union account, and making saving automatic through recurring transfers or split direct deposit. Published by the CFPB, a U.S. government agency.

authority: official-docs
supports: Lesson 03 — the emergency-fund size guideline and keeping the money in a safe, insured, accessible account.
key-fact: The SEC advises keeping emergency savings so "it will absolutely be there for them when they need it," with "up to six months" of income set aside by some savers, held in "safe places" such as "savings accounts, checking accounts, and certificates of deposit" that are "insured by the Federal Deposit Insurance Corporation (FDIC) or National Credit Union Administration (NCUA)."

authority: official-docs
supports: Lessons 04 and 05 — that high-interest debt compounds against the borrower and that clearing it outranks investing in the order of operations.
key-fact: "No investment strategy pays off as well as, or with less risk than, eliminating high interest debt." The SEC notes that "most credit cards charge high interest rates -- as much as 18% or more -- if you don't pay off your balance in full each month," and that "virtually no investment will give you returns to match an 18% interest rate on your credit card."

authority: official-docs
supports: Lesson 01 (the opening problem) and Lesson 03 — the scale of the missing-buffer problem in the general population.
key-fact: In the Federal Reserve's Survey of Household Economics and Decisionmaking, "the share who would cover a $400 emergency expense using cash or its equivalent also remained unchanged from 2024 at 63 percent" — meaning roughly one in three adults would not cover a$ 400 surprise from cash or its equivalent.

authority: official-docs
supports: Lesson 04 — that the APY a bank advertises on savings already reflects compounding, so it is the honest number to compare between accounts.
key-fact: "The annual percentage yield measures the total amount of interest paid on an account based on the interest rate and the frequency of compounding." It reflects "the relationship between the amount of interest that would be earned by the consumer for the term of the account and the amount of principal used to calculate that interest," expressed as an annualized rate. The Truth in Savings Act requires financial institutions to disclose the APY.

authority: official-docs
supports: Lesson 04 — that a credit card's APR is its yearly interest rate, the debt-side counterpart of a savings APY.
key-fact: "For credit cards, the interest rates are typically stated as a yearly rate. This is called the annual percentage rate (APR)." Interest can be avoided by paying the full balance by the due date. Published by the CFPB; last reviewed August 28, 2023.

authority: authoritative-guide
supports: Lesson 03 — the three-to-six-months guideline and keeping the fund liquid.
key-fact: "Financial planners often recommend the equivalent of three to six months of living expenses" for an emergency fund, kept in "a liquid (easily accessible), interest-bearing account like a savings account at a bank or credit union where you can withdraw your money at any time without penalty." Published by FINRA (Financial Industry Regulatory Authority).