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If you already have the cash and markets are not obviously overvalued, a lumpsum almost always beats a SIP on average, because every dollar starts compounding immediately instead of waiting in line. A SIP wins when you are investing out of monthly income, when you want to remove timing risk, or when a lumpsum would force you to buy at a single (possibly bad) price. The gap is driven almost entirely by time-in-market, not by cleverness.

A nominal return is the headline number your statement shows; a real return is what's left after inflation, and it's the only one that tells you whether your purchasing power actually grew. The exact relationship is real = (1 + nominal) ÷ (1 + inflation) − 1, not simple subtraction. At an 8% nominal return and 3% inflation, your real return is about 4.85% — so over 30 years your money grows ~4× in real terms, not the ~10× the nominal figure suggests.

Buying usually wins only if you stay put long enough — typically 5+ years — to outrun the large upfront transaction costs (often 8–10% of the price round-trip). The fast screen is the price-to-rent ratio: divide the home price by the annual rent. Under ~15 leans buy; over ~21 leans rent. A complementary check is the '5% rule': if yearly unrecoverable costs of owning (≈5% of the home's value — property tax, maintenance, and the cost of capital) exceed a year's rent, renting and investing the difference tends to win.

For the vast majority of people, term life is the right choice: it's pure, cheap protection for the years your family actually depends on your income, often costing 5–15× less than whole life for the same death benefit. Whole life (a permanent policy with a cash-value investment component) only makes sense in narrow cases — estate-tax planning, a lifelong dependent, or a maxed-out high earner wanting another tax-deferred bucket. The classic strategy is 'buy term and invest the difference'.

Lean FIRE and Fat FIRE are the same maths (about 25× your annual expenses) applied to very different lifestyles. Lean FIRE targets a deliberately frugal budget — often below the median household — so the nest egg is smaller and reachable sooner. Fat FIRE targets a comfortable or generous lifestyle, which can require 2–3× the corpus. The trap is inflation: because the target is a multiple of expenses, every extra unit of spending is amplified 25× and then inflated over your remaining decades.