The answer robotics gives is nonsense. If you are prepared to put in a bit of work, ask people etc etc, you will be rewarded.
A couple of points first off....ask lots of questions, however stupid they seem......the only stupid question is the one you don't ask !!!!!
Also, be patient. Don't over stock or stock too quickly and always keep up with water changes.
As for cost, you need to know what you want to keep. A fish only (FO) tank will cost you less to set up that a soft coral reef aquarium which will be less than a stony coral reef.
You will need salt, an RO unit (essential), a protein skimmer. good water circulation, good lighting (if keeping corals) filteration (usually live rock), test kits, hydrometer.
Those are the ABSOLUTE minimum you will need. Again, it'll depend on what you want to keep.
Try these sites
http://www.ultimatereef.net/forums/
http://www.phishybusiness.co.uk
Both will give you plenty of friendly, helpful advice.
Good luck and if you need any help.....ASK !!!