There's a harpist in my family, so I can tell you a lot about them.
Pedal harps are not cheap to buy - new ones can cost more than grand pianos. Lever harps are cheaper. If you can rent or borrow one, go for it. In some ways, it's quite similar to piano music: you often play bass clef with left hand, and treble clef with right hand. The red strings are C, and the black ones are F. At first, playing harp can be painful on the fingers. Tuning it takes time as well, and generally has to be done before every playing session.
If you can get good at playing harp, there's plenty of demand for harpists at weddings.
There are two main kinds: pedal harp, and lever harp. Pedal harps are huge and expensive, but can be easier to play: the way they work is that there are seven pedals, one for each of the note letters (A to G, although not in that order). Each pedal has a "flat", "natural" or "sharp" position, so if you set the A pedal to "flat", all the A strings play as A flat. Therefore you can change key by setting up the pedals. Lever harps have a small lever for each for each string, so before you play you have to set up the key signature on the levers. If you have accidentals in the music, you have to change the levers while you play. This can be quite difficult, a bit like turning pages.
A pedal harp is also difficult to transport, because of its size - a car such as a Volvo estate is needed.