Flat roofs can have a bad reputation for leaking, getting damaged and generally not being as sturdy or stable as a pitched roof. However there is no need for a flat roof to be any lesser quality than a pitched roof, as long as the roof is high quality and has been properly installed.
An older flat roof will often need to be replaced if it is leaking, or has holes or damage that could lead to leaks in the future. Modern flat roofing materials are far superior to older ones, so this is a good option in the long run. The initial cost will still allow the opportunity to save money, as there won’t be the high cost of repairs, potentially as an emergency if the roof is leaking, has become unstable or is unsafe. New flat roofs that are installed by professionals can be very hardy and durable.