I am selling my apartment in a co-ownership property. The managing agent (syndic) is charging me €500 for the état daté. Is this allowed?

No. Since 1 June 2020, a decree (No. 2020-153 of 21 February 2020) has capped the fee that a managing agent may charge for preparing the état daté at €380 including VAT. This document is required by the notary to complete the sale of a co-owned property and outlines the financial situation of the lot being sold.