In the central middle-salary Johannesburg scenario, living in the family home and delaying a car purchase for three years creates R602,000 more modelled net capital at age 25, and R3.32 million more modelled wealth at age 60, than moving out and financing a car immediately. The age-60 figure holds when the gap is preserved on the manuscript's common post-25 path.
Evidence status: Modelled. Sensitivity: high. Depends on GSX:HH-002:A01, GSX:HH-002:A02, GSX:HH-002:A03, GSX:HH-002:A04, GSX:HH-002:A05, GSX:HH-002:A06, GSX:HH-002:A07. This is a modelled counterfactual for one representative worker, not a forecast and not a statement that every graduate can or should live at home. The age-60 level includes a common 10% retirement-saving path. The manuscript treats the gap between strategies as the robust quantity, and the level as a scale illustration.
C01
Related questions
How does living with parents during the first years of employment compare with paying rent for a separate household?
What is the lifetime wealth comparison between delaying car ownership and buying a car at first employment?
7
Assumptions
Assumptions
These are the registered model assumptions. A result stays conditional on the ones a claim names.
A01Representative workerThe central case is a 22-year-old worker in Johannesburg, expressed in constant 2026 rand.22 years at the start
A02Middle starting salaryThe central worker earns R420,000 a year before tax. The manuscript also reports a lower case of R240,000 and a higher case of R720,000. These are illustrative starting salaries, not national percentiles.420000 constant 2026 rand per year, gross
A03Johannesburg housing bundleIndependent housing in the Johannesburg scenario costs R9,600 a month in rent and R7,200 a month in other housing basics. The manuscript treats these as transparent city scenarios, not estimated city means.9600 constant 2026 rand per month, rent
A04Contribution while living at homeWhile living in the family home, the worker contributes 12% of take-home pay, bounded between R2,500 and R6,000 a month, plus R1,200 of personal food and services. The manuscript counts this transfer as a private cost.12 percent of take-home pay
A05Financed used carThe car is a R230,000 used vehicle with a 10% deposit and 60-month finance at 11.5%, plus insurance, parking, fuel, maintenance, and depreciation as specified in the manuscript.230000 constant 2026 rand, purchase price
A06Hybrid transport while the car is delayedDelaying the car uses a public-transport and ride-hailing mix. In the central case the worker travels about 640 kilometres a month.640 kilometres per month
A07Common path after age 25At age 25 every strategy has moved out and acquired the modelled car. From then on the paths share the same real salary growth, a 10% retirement saving rate, and a 5% real investment return.5 percent real return per year
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Model
Model
The registered model statement. It is a scenario model, and the manuscript remains the full specification.
M01First-three-years household budgetThe model follows the first 36 months in monthly detail, covering salary, tax, household contribution, housing, transport, moving costs, and vehicle finance. At month 36 every strategy has moved out and acquired the modelled car. A common salary, saving, and return path then carries the age-25 gap forward. Differences at age 60 are attributed to the first three years.GSX:HH-002:M01
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Results
Results
Modelled scenario results. They are not forecasts.
R01-49000 constant 2026 randMoving out and buying the car immediately leaves a modelled funding shortfall of R49,000 at age 25 in the central case.Middle salary, Johannesburg, immediate independence
R02553000 constant 2026 randDelaying the move and the car for three years leaves R553,000 of modelled net capital at age 25 in the central case.Middle salary, Johannesburg, three-year delay
R03602000 constant 2026 randThe central three-year combined delay creates R602,000 more modelled net capital at age 25 than immediate independence.Middle salary, Johannesburg, three-year delay minus immediate independence
R043320000 constant 2026 randIf that age-25 gap is preserved on the common post-25 path, the manuscript reports R3.32 million more modelled wealth at age 60.Middle salary, Johannesburg, gap carried to age 60 at a 5% real return
R05486000 constant 2026 rand, housing-delay gap at age 25Staying at home for three years while buying the car immediately creates R486,000 more modelled capital by age 25. Moving out immediately while delaying the car creates R128,000.Middle salary, Johannesburg, housing delay versus car delay
R0615900 constant 2026 rand per monthThe modelled three-year home-only advantage disappears at a household contribution of roughly R15,900 a month.Middle salary, Johannesburg, contribution break-even
R072405 kilometres per monthUnder the central hybrid mix, a financed used car has a lower private monthly money cost only above roughly 2,405 kilometres a month. A 25% ride-hailing surge lowers that threshold to about 1,585 kilometres.Central hybrid transport, private money cost
Sensitivity
High · 4
Moderate · 0
Low · 0
Limitations
This is a modelled counterfactual for one representative worker, not a forecast and not a statement that every graduate can or should live at home. The age-60 level includes a common 10% retirement-saving path. The manuscript treats the gap between strategies as the robust quantity, and the level as a scale illustration.
The two effects overlap slightly when they are combined, because interest on positive and negative balances differs. The split is a central-scenario comparison, not a rule for every city, salary, or commute.
The threshold is a diagnostic for this scenario. The manuscript does not present it as a fair-rent recommendation. A higher contribution can still be the right family choice while no longer raising the worker's private wealth.
The comparison is private money cost. It does not price safety, reliability, waiting, shift work, or access to a job. A 25% ride-hailing surge moves the modelled threshold to about 1,585 kilometres a month.
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Claims
Claims
Each claim names the assumptions it uses and the limitation that travels with it.
C01GSX:HH-002:C01In the central middle-salary Johannesburg scenario, living in the family home and delaying a car purchase for three years creates R602,000 more modelled net capital at age 25, and R3.32 million more modelled wealth at age 60, than moving out and financing a car immediately. The age-60 figure holds when the gap is preserved on the manuscript's common post-25 path.Modelled · high sensitivity
C02GSX:HH-002:C02In the central case, staying at home for three years while buying the car immediately accounts for R486,000 of extra modelled capital at age 25, while moving out immediately and delaying the car accounts for R128,000. The housing decision is the larger of the two.Modelled · high sensitivity
C03GSX:HH-002:C03The modelled advantage of three years in the family home disappears when the household contribution reaches roughly R15,900 a month in the middle-income Johannesburg case.Modelled · high sensitivity
C04GSX:HH-002:C04Under the central hybrid transport mix, the financed used car has a lower private monthly money cost only above roughly 2,405 kilometres a month.Modelled · high sensitivity
Sources and reproducibility
The PDF and complete Markdown source are both published.
Full manuscript: 6 107 words across 48 indexed headings. Source checksum: abf1b1d2f004…. Code recorded: yes. Data recorded: yes. Environment recorded: no. Published files: 4. the published statement does not rely on a recorded random seed A public code repository is not published.
