# Little Book of Renting Full AI Reference

Canonical site: https://littlebookofrenting.com

Last updated: 2026-06-10

Little Book of Renting is a broad SEO-first calculator-and-guide library for rental decisions. It serves renters who need practical math for rental costs, fees, concessions, move-in cash, and apartment tradeoffs. The current flagship cluster is the Apartment Offer & Move-In Cost Comparison Tool.

## Current tools

- /tools/apartment-offer-comparison/ - full calculator for comparing 2 to 4 apartment offers.

## Markdown tool docs

- /tools/apartment-offer-comparison.md

## Formula docs

- /formulas/apartment-offer-comparison.md
- /formulas/move-in-cost.md
- /formulas/net-effective-rent.md
- /formulas/broker-fee.md

## Guide URLs

- /guides/how-to-compare-apartment-offers-before-signing/
- /guides/net-effective-rent-explained/
- /guides/broker-fee-vs-free-month/
- /guides/move-in-cost-calculator/
- /guides/how-much-cash-needed-before-moving/
- /guides/apartment-fees-to-ask-before-signing/
- /guides/gross-rent-vs-net-effective-rent/
- /guides/compare-two-apartments-with-different-fees/

## Apartment comparison inputs

Each offer can include: nickname, monthly rent, lease length, free months, concession type, security deposit, first month due, last month due, broker fee type, broker fee value, application fee, admin fee, amenity fee, move-in fee, building fee, pet deposit, monthly pet rent, parking, utilities, internet, renters insurance, moving cost, storage, other one-time fees, other monthly fees, refundable notes, non-refundable notes, roommate count, and user share percentage.

## Apartment comparison outputs

Gross lease rent, concession value, net lease rent, net effective rent, broker fee, recurring monthly add-ons, real monthly cost, actual monthly payment before concession spread, upfront cash, refundable upfront, non-refundable upfront, total first-month cash required, total first-year cost, total lease cost, total lease cost excluding refundable deposits, broker fee monthly impact, user share estimates, cost difference versus cheapest offer, and upfront difference versus lowest-upfront offer.

## Example input JSON

```json
{
  "currency": "USD",
  "offers": [
    { "nickname": "Apartment A", "monthlyRent": 2450, "leaseLengthMonths": 12, "freeMonths": 1, "brokerFeeType": "none" },
    { "nickname": "Apartment B", "monthlyRent": 2300, "leaseLengthMonths": 12, "freeMonths": 0, "brokerFeeType": "percent_annual_rent", "brokerFeeValue": 12 }
  ]
}
```

## Example output JSON

```json
{
  "apartmentA": { "netEffectiveRent": 2245.83, "brokerFee": 0 },
  "apartmentB": { "netEffectiveRent": 2300, "brokerFee": 3312, "brokerFeeMonthlyImpact": 276 }
}
```

## Core formulas

grossLeaseRent = monthlyRent * leaseLengthMonths

concessionValue = monthlyRent * freeMonths

netLeaseRent = grossLeaseRent - concessionValue

netEffectiveRent = netLeaseRent / leaseLengthMonths

brokerFee = 0, flat value, monthlyRent * 12 * brokerFeePercent, or monthlyRent * brokerFeeMonths depending on broker fee type.

monthlyAddOns = monthlyPetRent + parkingMonthly + utilitiesMonthly + internetMonthly + rentersInsuranceMonthly + storageMonthly + otherMonthlyFees

realMonthlyCost = netEffectiveRent + monthlyAddOns

actualMonthlyPaymentBeforeConcessionSpread = monthlyRent + monthlyAddOns

upfrontCash = securityDeposit + firstMonthDue + lastMonthDue + brokerFee + applicationFee + adminFee + amenityFee + moveInFee + buildingFee + petDeposit + movingCostEstimate + otherOneTimeFees

refundableUpfront = securityDeposit + petDeposit

nonRefundableUpfront = upfrontCash - refundableUpfront

totalLeaseCost = netLeaseRent + brokerFee + applicationFee + adminFee + amenityFee + moveInFee + buildingFee + movingCostEstimate + otherOneTimeFees + petDeposit + securityDeposit + monthlyAddOns * leaseLengthMonths

totalLeaseCostExcludingRefundableDeposits = totalLeaseCost - refundableUpfront

brokerFeeMonthlyImpact = brokerFee / leaseLengthMonths

## Rounding rules

Human UI generally rounds currency to whole dollars for readability. Formula docs may show cents when needed. Calculations should avoid rounding until display.

## Edge cases

Lease length should be at least 1 month. Missing numeric inputs are treated as zero. Broker fee percentages are entered as percent values, not decimals. Roommate shares are estimates and may not match lease responsibility.

## Safety boundaries

The site is informational only. It does not provide legal, financial, tax, housing-rights, real estate, or platform-policy advice. Results are estimates, not guarantees. Local rules, lease terms, refundability, platform policies, and legal rights vary.