Mitigate damage as soon as it is safe to do so. Coordinate with your insurer, who will likely decline. Get in touch with your local FEMA representatives to see what assistance might be available.
@Shu Zhu How deep was the water? Were they occupied? How many units do you have? If you have the money and don't have to wait for insurance move very quickly because there is going to be a major shortage of housing?
If you do not have the money you should be able to get an SBA low-interest loan via FEMA to rebuild.
