Details of the Help To Buy scheme, which I announced in Budget 2017, are set out in Finance Bill 2016 which was published on 20 October. The Bill provides that, in the case of a self-build residence, a first-time buyer must take out a mortgage in an amount which is at least 70% of the valuation of the residence as approved by the mortgage provider.
The calculation of the 5% referred to by the Deputy is also based on the valuation of the residence as approved by the mortgage provider.
While I cannot comment on the specific case referred to by the Deputy, there wouldn't appear to be any reason why the individuals concerned could not make a formal application to Revenue in January 2017 when the Revenue online system for the Help To Buy scheme is due to come on stream.
Further information in relation to the scheme is available from the Revenue website at http://www.revenue.ie/en/index.html.