Buildings occupied for periods between a few months to a few years and converted into temporary offices donated to local non-profit organizations. Landlords in Brussels, London, Milan, and Barcelona who cannot begin construction work on their properties because they are waiting for permits are approached by PRECARE for permission to occupy the building for a fixed period. A contract is signed with the landlord obliging the tenants to cover utility costs, but not pay rent. Many non-profit projects depend on rent-free space. In 2007 there were estimated to be 15,000 unoccupied buildings in Brussels alone. The Belgian group PRECARE has transformed buildings awaiting renovation into temporary offices since 1999.