The purchase of a condo leased to a third party is a frequent occurrence in the resale market. Save for an agreement to the contrary, nothing prohibits a co-owner lessor from selling and a purchaser of purchasing an apartment even though the tenant wishes to continue to reside in it.
The lease is attached to the immovable, not to the co-owner/ lessor. The lease will continue to be in force even if the unit is sold and the terms and conditions of the lease shall remain the same.
The resolutions of the General Meeting of the co-owners require complex calculations in order to determine whether a the required majority has been reached. To do so, you must make sure that the register of co-owners is up to date, and that the compilation of votes is done according to the relative value specific to each fraction. This reduces the risk of contestation of an adopted resolution. That said, some decisions have extremely important consequences for all co-owners so the requirements in terms of majorities are then higher. For this reason, the law imposes three levels of majority: absolute, enhanced and double majority, depending on the importance of the decision to be taken.