Potential figure of 13.7 million migrants was estimated over a longer period than suggested.
Most people are homeowners by the age of 36, but the average first-time buyer is younger.
The proportion of those aged 65 or over paying income tax was 62% in the year ending March 2023.
The £2,000 suggested is based on figures produced by the Conservative Party which the Labour Party has disputed.
The money will not just be spent in the North and the Midlands, despite the proposed line operating from Birmingham to Manchester.