Leigh, It depends on the type you want to set up.
In my opinion, there are only two types of tanks to keep. If you just want the pretty fish, and a couple of pretty white dead corals, you can do a fish only tank. This requires no more than adding salt to your water, and using a different substrate. It uses mechanical filtration just like freshwater tanks. The lights typically found on freshwater are usually adequate also. Salt for making water will run about 25 dollars for a bag that makes 50 gallons. The substrate, usually a crushed coral, is roughly one dollar a pound. It typically comes in 25 pound bags. So you get your bag of salt, crushed coral, throw it all in a 40 gallon aqurium, cycle it, add your fish. I am simplifying a bit, but there you are, 50 dollars. Downside is, You will be doing constant water changes,($), and forever be seeing cool things you can't keep.
A reef tank. There are two kinds. The biggest you can afford, and Nano reefs. Nano reefs are generally under 20 gallons, and quite frequently, as small as 2 1/2 gallons! Bad things happen real fast here! Nano reefs are the betta bowls of reefkeeping, and not my thing. You are very limited.
Ok Get yourself a big tank, let's say 90 gallons. Here is a list of the minimums to get started;
Substrate, 4-25lb bags
Live sand, 2-10lb bags
Base rock, 30-40lbs
Live rock, 60-90lbs
The biggest rubbermaid tub you can fit inside the cabinet stand.
A canister filter,
Two submersible heaters
Two powerheads in the 150-300gph range
One good submersible pump. 600-800gph range
lighting capability of 500-800 watts
Someone in house that is very adept at putting things together
This will get you up and running. You will have more to add later as your tank matures, skimmers, uv sterilizers, calcium dosing, more lighting..
Cost is the issue in the beginning, but a reef tank is rock solid in its stability once it gets stable. You don't have excessive water changes, or a whole lot of maintenece once it is going well if you just want to hold status quo.
Base rock is pennies a pound, not an issue. The salt is an expense at first, but no more than a fish only tank. The substrate,(crushed coral), needs to be four inches deep in a reef tank, hence the four bags, maybe a little more even. The live sand will run about two bucks a pound. It is very beneficial in getting "critters" growing in your sand bed.
The two most expensive items in a reef tank are without argument, live rock, and lighting. Look hard and long, you'll find live rock for three to five dollars a pound. Not at all strange to pay almost nine bucks a pound. If you buy in quantity, you get a better deal. Lighting....If you do it yourself, you can achieve satisfactory lighting goals for about 200 dollars. That includes building a canopy. Buy it ready made? 600-1000 dollars.
Sorry I skipped around a bit. I left out some info, but this should give you some ideas on price.
My advice. Find a reef club in you area. All fishkeepers are tight knit bunches. Reefers even more so. I know of clubs that even get together every month or so to make their own food! They could most likely give you fair advice on who to deal with in the area. Check auctions. I have seen whole systems sell with livestock and all for less than the live rock alone is worth.
After all the money I spent, I don't regret it a bit.
