In a measure Treasurer Rob Lucas says he's happy to defend, the government will remove a tax loophole that currently allows investors with multiple properties to pay little or no land tax.

The change will levy tax according to an owner's interest in every piece of land rather than the properties held within the same ownership structure, such as a company or family trust.

It's expected to net the government an extra $40 million a year once it takes effect in July 2020.

"This measure is aimed squarely at closing a loophole that may encourage some landowners to form complex ownership structures designed purely to avoid paying tax," Mr Lucas said.

"We don't think that's fair and we will be introducing a model that works well interstate."

But, despite previously announced cuts to the rate of land tax, the measure is sure to be resisted by the property sector amid fears the increases could be passed on in higher rents.

At the other end of the scale, the government has also announced a $105 million package to help those seeking to enter the property market, including $21 million to build about 90 SA Housing Authority homes and other cash to fund $10,000 interest-free deposit gap loans.

Mr Lucas said the loans were expected to leverage about $60 million in new lending and lead to the construction of about 170 homes, providing a boost to local builders and tradies.

"This is a deliberate and targeted response to the well-documented challenges faced by the local construction industry and the many South Australians who may be finding it difficult to break into the housing market," the treasurer said.

"This will help ensure the great Australian dream of home ownership is a reality for more."

Australian Associated Press