Clarinets may be made of wood or plastic, both having metal keys. Good clarinets can be expensive, so you may want to hire one until you are sure you are going to persevere with it. Many music stores have good clarinets to rent, and some also have hire purchase plans.
If you are buying a second–hand instrument, there are a couple of things to look out for. First make sure there are no dents, bends or cracks in the instrument, as this will affect the tuning. Also check for leakage by asking someone to play over the range of the instrument to see whether all the notes sound properly. If possible, have a professional check out the instrument before you buy it.