The plan is to develop the 12-acre site of the former Queen Mary School into 164 new homes.
Regeneration Liverpool will now seek planning permission, with the aim of starting construction later this year.
Under the terms of the development agreement, it will generate income to Sigma of around £800,000 over the next five years.
The homes will be marketed though Countryside Sigma, Sigma's joint venture with Countryside Properties.
Regeneration Liverpool is also already developing other sites across the city, including more than 700 homes at Norris Green. Sites under option include the Stonebridge Cross and Lime Street/Knowledge Quarter developments.