I do weekly water changes of 10% on my 55 gallon tank. I also have around 65 pounds of live rock and 80 pounds of live sand. I also have a Hang on the Back Protein Skimmer (Reef Octopus BH-1000). I am running a heater that is for 75 gallon tanks, and I have two power heads rated for 55 gallon tanks (One on each side).
I am running a fluval 206 canister filter right now. I am going to upgrade to a sump tank. I had it from my 29 gallon saltwater tank. I upgraded to the 55. I have been using a canister filter without any problems, and I am thinking about just keeping it on my saltwater tank even with a sump. It helps keep my water clear, and I like that.
Most people say a build up nitrates can happen, but I never had it happen. I do clean it out once every two weeks. Just a normal cleaning in dirty tank water to not kill the bacteria on the filter sponges.
As for cost. I am afraid there is no way around it if you want to start out with a successful tank. When I started my 29 gallon tank, I saved up to buy all the equipment and live rock and sand.
You can get uncured live rock, and that will be cheaper than rock already cured. What you would do is set up your tank with all your equipment and get everything running. Order your live uncured live rock online and it should be shipped overnight to you. You will set up the rock as the way you want it. The die off from the rock will cycle your tank!!! :-p You will need water movement (Powerheads) and you will need to do PWC
each week until your tank is fully cycled.
Once cycled you can add your fish. Slowly of course! I put two in the first time. I waited about a week and tested my water each day. I put one more in, and after a week I added my last fish.
A saltwater tank is a little more involved than freshwater, but I have found (coming from freshwater) that it is not to difficult when done right the first time! So far I have been successful!! (Knock on wood) :-/ This is my 55 I upgraded to a month ago. From the 29 gallon I had!!