The biggest difference between a FO(Fish Only) tank and a Reef tank IMO is the lighting. Your initial cost of running lighting for a reef tank can be a lot more expensive than running a FO tank. The maintenance cost, replacement bulbs, will also cost more for a reef tank than a FO.
There are many things to consider when buying a lighting system to fit a reef tanks needs. First you must know what you want to keep in your reef tank. Whether it be certain corals, anemones, clams etc. that require lots of lighting, mid-range lighting, or very low lighting to thrive. After that is determined you must look at the size and depth of the tank you will be using. ie. is it shallow enough to use a few low wattage VHO (Very High Output) lights; is it so deep that only a high wattage MH (Metal Halide) can successfully penetrate down to the aquarium floor? You must ask yourself these questions along with many other considerations to take into mind. The best thing to do is educate yourself. Learn about reef life, reef organisms big and small and what role they play in maintaining a successful reef. Read this forum and buy yourself a reef book.
I'd recommend "Natural Reef Aquariums" By John H. Tullock
Good Luck
Mike