The property developing Deague family have spent $86 million on a 70 hectare house and land site near Craigieburn.

They have the intention to build a $750 million estate.

It's a rare house and land purchase for the Deague family, more well-known for their apartment, hotel and mixed-use developments.

Last year the Deague's paid nearly $25 million for a commercial development site in South Melbourne.

That's set for a $150 million, seven level Rothe Lowman-designed office project next to its existing business park.

The Deague family claims a property development tradition in the state that dates back to 1859.

Deague Group chief executive Will Deague told the AFR they saw better opportunities in the house and land market but the family is still committed to the apartment and mixed-use development space.

"The returns [in apartments] aren't there and so the demand has softened," Deague said.

"With migration into Australia, and especially the northern corridor of Melbourne at record levels, we will continue to look for further opportunities in this space," he said.

William Deague recently spent $12.2 million on a 1930s Toorak home and quickly got the work demolishing the landmark home.

The Deague family launched Whitehorse Towers in Box Hill late last year and saw over 500 apartment sales in two days.

The towers were billed as the tallest residential towers outside of the CBD.