Keeping salt water fish is the same as keep fresh water fish. You do not need any expensive equipment. You can keep salt water fish with the same equipment you keep fresh water fish. You just need to keep up with water changes. It's not 10x harder. The only difference is that you have to add salt. Make sure you check salinity, ph, nitrates, nitrite, amonia, and temperature. As long as you keep up with water change you'll keep all of those under control.
Salt water fish still get sick if you don't feed them corectly and don't keep the tank clean.