I've had tanks all my life ranging in size from 2-100 gallons. The tank for sale was my first attempt at salt water. We ended up moving before the tank finished being established and it didn't make it. We moved into a smaller house and just don't have room for it. Salt water tanks are much more interactive and fun to own, but more work as well. The major difference between salt and freshwater tanks is that once you get a salt water tank balanced and settled, you will rarely (very rarely) have to clean it.
Tanks are a ton of fun for kids and fresh water tanks give you instant satisfaction. Dump in your substrate, place any structure or decoration you want, and dump in fish. Boom, you have a fish tank. With salt water tanks its a long term commitment as the tank takes a long time to settle, up to 6 months or even a year.
If this is your first tank, and it sounds like it is, I would suggest going freshwater. You'll learn a lot and if you ever want to take the next step you'll have a lot of foundational knowledge that will help with saltwater.
The tank is still for sale though! It literally has everything you will ever need for a saltwater tank. All you'll have to add substrate and water. I'll get some pictures tonight.