Many have posted solid advice about how to proceed with flooded property.
@David S. posted a great list of points to consider. Here are a few more.
Your most immediate need is to file your claim if you have insurance and then to get to work gutting and drying the structure. Do not cut corners on this especially if you had flood insurance. It is recommended to gut to at least 1' above the water line and remove any wet material. You don't need to pay a high priced contractor to do this work, but you at least need one supervisor or yourself who can oversee the work and make sure big mistakes aren't made.
Do not think you can get away with keeping base cabinets and saving existing tub surrounds if the water got that high. That will only trap mold and cause problems for you in the future. I had to overcome this thinking too and decide to do full gut outs and replace everything that was affected.
Housekeeping goes a long way, so keep everything really clean and swept for the most efficient drying and decontamination.
HIRE A PROFESSIONAL to decontaminate or treat for mold and get a certificate. You will be glad you did this especially if there is a chance you will go to sell this previously flooded home. Also get a building permit. It is tempting to bypass this step especially if you are dealing with multiple units and don't normally pull permits, but there are too many risks to not getting a permit.
Hire a 3rd Party Insurance Adjuster who works for you and NOT the insurance company. In most cases they do not get paid until you get paid. Hire this person prior to re-construction and you will be glad you did because in almost all cases they will get you paid substantially more than the insurance adjuster says your claim is worth. PM me for a recommendation on a great 3rd party adjuster if you need one.
Private Market Flood quit writing new policies in Baton Rouge and flood insurance was more expensive here for the first 12 months after the flood. A year later, private market has reopened and rates are still affordable. If you buy flooded homes and private market flood is not available, get a flood elevation certificate from the seller and make sure the property is not 1' or more below base flood elevation. The lower you are in relationship to the base flood elevation, the more expensive your flood policy will be. Of course being above base flood elevation is ideal if you are buying flooded homes.
Do not pay a contractor in advance of any work. EVER!!!! I made this mistake a couple times and will not do it again.
Houston area residents will witness an outpouring of support and help from neighbors showing up to lend a hand. People will be cooking giant pots of jambalaya and passing plates out to neighbors working to restore damage. Church groups and volunteers will show up to help folks who don't have help to get their properties gutted out. Friends will house friends as well as strangers in need of a roof and a bed. People are generally resilient in these situations.
If you are looking to expand your business, do not be fearful of what is to come. Take advantage of this opportunity to pick up some really great deals and make intelligent decisions about what and where to buy. There are usually several silver linings to be found in an event like this. While many homeowners will be devastated and not have the means to rebuild, many others will, after some hard work and sacrifice, be able to move back into the newly remodeled home they only wished they had before the flood. Look for the silver lining and try to figure out why this happened for you rather than to you. Prayers from Louisiana going out to all of you who are impacted.
See you at the top!