Under the joint venture, 4DS will manage all third party online advertising for Freeads.co.uk including online media, partnership emails and sponsorship with third parties across the site.
The move is in line with Freead's plans to treble the number of ads on the website in coming months, according to chief executive Duncan Horton, formerly marketing director at lastminute.com.
Freeads is the fastest growing classified website in the UK, hosting 62,000 unique ads a day and with more than 1m users per month. Data from analysts at Hitwise puts its market share at double that of Loot.com.
The website launched in 2001. It is backed by Clive Jacobs, founder of car hire giant Holiday Autos, who bought a major stake in the business in early 2007.