By "Live Sand" I believe you want sand that is "seeded" with many tiny lifeforms, in addition to beneficial bacteria. This sand is "alive" and like LR is kept in clean heated seawater at all times.
This site sells 'Florida Keys Natural Live Sand' which sounds close; I'd make sure it is shipped wet before buying. If not, many other online suppliers also sell it. Expect to pay about $3.50* lb shipped. Plan your sandbed to be several inches deep to maximize the denitrifying capabilities of the LS. This is just one of many ways LS can benefit the health of the marine tank.
RO units can also be bought online, or at your local Costco. Many shopping centers now have "water stores" or vending machines that perform RO* DI on the local tapwater and sell it for as little as .20* gallon. This works but is not too conveinent. The tapwater purifying unit dathem spoke of performs DI (De-Ionization) and works well unless you have hard water. If so, expect to get possibly quite a bit less than the 50-150 gallons per cartridge.
Carbon removes many organic compounds, including those that cause yellowing and strong "fishy" odors. Don't leave it too long; 5 days is plenty then remove. You can go without for a week or 2, then add more. Carbon will also remove trace elements, so regular water changes and* or supplementation ensure proper levels. Carbon is great for removing medications and other toxins such as trace amounts of household pollutants.
YBYW.