The UK's third biggest property portal, OnTheMarket.com, plans to raise £50m by issuing shares on the stock market.
It will use the money to help it compete against its larger rivals Zoopla and Rightmove, which currently dominate the market.
OnTheMarket.com is owned by over 2000 estate agents, including Savills, Knight Frank and Strutt & Parker.
It has previously accused Zoopla and Rightmove of charging too much for advertising properties on the internet.
"For consumers and agents alike, we are committed to creating a genuine agent-controlled alternative challenger business and brand to the two leading incumbent portals," said Ian Springett, chief executive of the parent company Agents' Mutual.
The money will be spent on a "heavyweight" advertising campaign on television, and in digital and print media.
OnTheMarket's members will vote on 6 September whether to go ahead with the float, which if successful would value the company at between £200m and £250m.
The offer will be open to institutional investors only.