The pilot housing scheme at Maghon Park, the former Army camp on the Mahon Road, is the first of its kind in the UK and is aimed at first time buyers.
It was officially opened by Minister for Social Development Margaret Ritchie, who described it as an "innovative and imaginative solution to get people onto the property ladder and keep them there".
She told a waiting group of press, local politicians and representatives of groups involved in the development that she hoped the Portadown project would also be rolled out in other parts of Northern Ireland, and commended those organisations involved.
The Own A Home scheme is a joint initiative between the Government, Portadown builder and developer Turkington's, Clanmil Housing Association, the South Ulster Housing Association, and Barclays.
The development, known as 'Clendinning at Maghon Park', consists of 127 former Army houses - 24 detached houses and 103 semi-detached - with both three and four bedrooms, and all with garages.
Prices start at £145,000 for a three-dedroom semi-detached. A four-bedroom semi-detached is £155,000 while a typical three-bedroom detached is £185,000 and a four-bedroom detached is £199,000.
Under the scheme, buyers will not have to pay a deposit. They will buy 50 per cent of the value of the house through a 100 per cent mortgage from Barclays. Turkington's will pay 25 per cent of the cost of the house, with the remaining 25 per cent provided by either of the housing associations.
The 15-year old houses were bought by Turkington's earlier this year and are being sold through BTW Cairns and local estate agent, The Property Spot, based on the Armagh Road.
Jim McKeag, managing director of Turkington's, said, "The houses are competitively priced and have a garage, gardens and a brick-paved driveway.
"Clendinning is just minutes from the centre of Portadown and this established development of 127 homes is convenient to schools, shops and leisure facilities, so all round it is a fantastic opportunity for the first-time buyer."
The initiative means that anyone buying one of the three-bedroom semi-detached houses at £145,000 would not have to find an initial 10 per cent deposit of £14,500.
According to the Department of Social Development, on a typical mortgage of £145,000, buyers would need to put up a 10 per cent deposit and then pay a typical rate of £199.61 per week mortgage.
Under the Clendinning scheme, buyers pay a typical rate of £109.85 per week mortgage and a typical rent of £38.06 per week, amounting to £147.91 - a weekly saving of £51.71.
The buyer can, at any time, buy a further share in the property, either outright or in stages. Alternatively, if they wish to move, they are able to sell their share on the open market.
Trevor Kerr, valuer and sales negotiator of The Property Spot, said two great advantages of Clendinning were the maturity of the development and the gardens and the considerable amount of storage space in the houses.
He said, "If you are buying a property in a new development you have to plant out your garden and, in some cases, put in driveways. Here, even the paths are brick-paved. The houses are all ready to walk into. It's like taking a new development and fast forwarding it 15 years.
"The benefits of only buying half the house now is that first time buyers often haven't been in their jobs for long. As their prospects improve, their salaries improve and they can buy back a bit more if they wish."
He added, "This initiative will help fill the gap left by the shelving of the Co-ownership scheme. I think it's what first time buyers have been waiting for. When the Co-ownership scheme stopped, many first time buyers stopped buying."