Unlike other instruments which squeak or just plain don't play when you are first learning, the harp always makes a beautiful sound right away. It doesn't take too long to learn to play simple tunes. However, just like most things worth learning, the harp can become quite difficult if you want to learn to play it well. Harps are also available for rent, and can be built from kits. Besides the purchase price of the harp, you will also need to buy new strings every year or two, have the harp maintained regularly, and buy extras like covers and a harp transport dolly.
Insurance is also an excellent idea.
As you can see, the harp isn't cheap. Listen to harp music and try to go to harp concerts. Talk to a harp player if possible. Make sure that this is the right instrument for you. You can either learn by teaching yourself or by finding a teacher.