At least 20 MPs own rental or commercial properties, and many more own at least two properties for their own use.
An outline of the financial interests of all 122 MPs was released in the Register of Pecuniary Interests on Tuesday.
The register identifies MPs' interests in property, companies and trusts, as well as any secondary employment and gifts.
It is designed to help protect MPs from claims of a conflict between their public duties and private interests.
The register shows that most MPs have an interest in a trust, but does not reveal any details of the trusts' activities or holdings.