In order for a real estate sign to be visible, real estate professionals often want to place it on the condominium’s common property. However, some condominiums prohibit real estate signs (for example, for sale signs, for rent signs). Other condominiums allow you to post signs with permission, while others specify exactly where you may post such signs. Check your condo bylaws or rules. You can also ask the management company. For self-managed condos, check with your condo board.