Short answer: A 14 gallon is fine, but the saltwater hobby is a huge moneypit and you'll never be able to get even a fraction of what you spend back by selling your livestock when you get out of the hobby.
Long answer: The BioCube 14 has really crappy lights and you'll only be able to keep soft corals and LPS. No fun stuff like anemones, clams or SPS when you get ready. I would really encourage you to go with a BioCube 29 HQI, which is lit with metal halides. Those will keep ANYTHING you want alive, clams, sps, anemones, ect... They're just great.
My advice: Unless you have your heart set on it, it's a really big money pit to get into and you can't make any money by just selling corals like people say. You have to spend money on electricity to run the tank, you have to buy salt and RO/DI to mix water (natural seawater isn't good for a few reasons which I won't get into), you'll want to buy corals, fish, ect. I'm not trying to discourage you, I'm just warning you, you'll spend a lot on the hobby. I just got out because I found out that I get just as much joy out of Nepenthes and they're less expensive. You don't have to get anything for them except for RO/DI very rarely, and if you have them in a terrarium or greenhouse, you have to pay to light/heat/cool that. Nepenthes grow a lot faster than coral too. Some corals do grow really fast, but they don't grow nearly as fast as you would want them to. To get the overgrown tank look that everyone wants, you have to stock it heavily and wait five years while keeping up with maintenance to make sure everything is perfect. You'll also run into a lot of problems with your tank, like heaters blowing up, equipment failing, algae, not enough water flow, ect... It's all just a mess. But there are thousands of people who do a really good job at the hobby and can keep up with the stuff financially, so it's something to look into. Another hobby I wish I would have gotten into was dart frogs, so if you're just looking for a new hobby in general, dart frogs are a cool thing to check out.
HTH!