Being both a electrician, contractor and lifetime resident of New Orleans, I figured I'd drop my two cents. A.) All this sarcasm and shit talking about flooding again is really counterproductive to any discussion I would expect on Slashdot. Depending on where in New Orleans the house is it could never flood again. I would say that even during the May flood of 1992, only perhaps 25% of houses got ANY water in them, and it was more like inches to a foot. Katrina was a catastrophic collapse of everything that has protected the city since the turn of last century. I wouldn't expect it to happen again within your resale window.
B.) When I wired my personal house, I put Two RG6 coax and Two Cat5 into every comm. box, two in each room. I used Leviton's superbly overpriced termination equipment and plates for the walls. Since it was a smaller house, I didn't have a closet to make a heated and cooled "equipment room" so it had to go in the attic. I have a DSL modem going into a Linksys wireless router, then going into a 16 port linksys switch. It has been up and running for about 4 months and it is perfect. Oftentimes when my brother and sister are at home, there are five or more computers on the wireless, friends on the deck and in the trailer on wireless, etc.
I also put 5.1 surround in the living room, in the walls (just for the two rear surrounds). The room was a little too small for the rear surrounds, plus the framing of windows and doors behind the viewing area would have made it tough.
The touch that really makes my day is a set of boston acoustic 5.25" speakers in each of the bedrooms and the dining room, a pair of polks outside facing the deck, and a off the shelf switching system. I bought one of those microwave cabinets and placed the switch and a separate reciever in it, so with the interior walls insulated like they are you can watch TV in the living room (surround) and blast music in all three rooms and outside without any interference between the two.
C.)As far as placement, like I said, I put about two in each room, just to be safe. I have one Cat5 for the phone, one for ethernet. One upstream cable, one down stream. I put a modulator on the back of the main living room TV, sent it up the upstream cable hookup to a amplified splitter so everyone in the house can watch Sat, even without a receiver. I put a Communications Outlet (CO) above the kitchen counter, one behind the refrigerator to serve either a fridge TV or a media center for the whole house audio, and two in every room but the bathroom.
D.) In hindsight I would have put a weatherproof set outside on the deck, one in the bathroom up high for a TV, and I would have put RCA's between the whole house audio amp and the home theatre home amp.
The final cost I would estimate to be around 500-750$ but I also had a few peices. Again, this cost is for me doing it myself, another electrician would have charged more, and the specialty contractors that do this kind of work even more than that.
Please feel free to contact me if you have any more questions about my setup, some specific advice relating to your exact setup, or even if you want some help, I can give you a price (for Slashdot members!) just above cost. My email is mikelj@gmail.com. Good luck, and thanks for helping to rebuild the NOLA.
