See here.

Your nose knows!

Take a look in attics and basement corners. A knife blade into suspect wood framing will reveal the extent of wood rot. Peeling paint and wallpaper are giveaways too.

Determine the source of the water.

Heads up! Before the ceiling collapsed, just a few cracks and water drops. If there are watermarks on the ceiling, insulation will likely have to be replaced as well.

And if it has been remedied. Make any offer subject to an inspection by a mould specialist.

I asked for a quote for mold and thermal inspections we will see what they come up with. The upper floor water damage might be from roof leaking, but I am not sure about lower floor ones, especially since they said water can not be turned on. And the house didn't smell musty or something like that, it smelled fine.

Make sure you also check for termite, current and previous infestations.

Run from the house. its going to be costly to fix. whether its faulty piping, a leaky roof, or water coming from the foundation. it’s a ridulously expensive fix. take it from me, run from that house.