Find the source before cosmetic repairs
Roof leaks, plumbing above the ceiling and HVAC-related water can all create similar stains. Repainting before fixing the source only hides the symptom.
Sagging can mean significant saturation
A bulging ceiling may be holding water or may have lost structural integrity. Keep clear of unstable material.
The cavity above may also be wet
Insulation, framing and adjacent wall areas can retain moisture beyond the stain.
Drying and repair come after source control
Once the source is stopped, the affected assembly can be evaluated for drying, removal and repair.
Talk through the situation by phone
Describe the source of the water, the affected area and whether the water is still entering the property.