The Help to Buy Mortgage Guarantee allows you to buy a newly built home or an existing property with a deposit of 5% of the asking price of the property.
The purpose of the Help to Buy Mortgage Guarantee scheme is to provide lenders with a government guarantee on loans to people with a deposit of between 5% and 20%. This is designed to increase the supply of more high loan-to-value mortgages in the system.
As with the other elements of the scheme this is available to first time buyers and existing home owners.
The maximum value of the loan is up to 600,000 and more information can be found here : http://www.helptobuy.org.uk/home-ownership-schemes/help-to-buy-mortgage-guarantees/