The most common reason for a child, teenager or adult to give up learning how to play a guitar is that it is unplayable. The strings are to high and it does not stay in tune. My advice is hire one from your local music instrument supplier. Before you do check whether the supplier offers teaching and if they are involved with the local schools. If not find one that is. Suppliers involved with teaching are unlikely to hire unsound instruments. If progress is made then purchasing a new or second hand guitar is viable. Again your local dealer will be able to guide you. They may have a number of pre-owned instruments that previous learners have outgrown.
These basically come in two types, Nylon or Steel strung. The most commonly used for learning are nylon strung as the strings are wider apart and easier to press down than steel strung. Nylon strung is usually associated with Classical, Flamenco and Latin styles (Rumba, Salsa, Tango and Gypsy Jazz) but are also used in folk, country, blues and many other styles.
Nylon String Example: This model is one of the better models available, Fender ESC80 Educational 3/4 NT. The 3/4 means it is slightly smaller than normal making it most suitable for the 10 – 14 year old. If you would like to know more about this model click here.
Steel Strung guitars: When the pupil has mastered the basics on the nylon strung guitar then it might be time to move onto the steel strung variety. They are harder to play as the strings have a higher tension and are closer together. Once again I would advise hiring and if progress is being made then you might consider buying. It is important that the guitar is playable and has good intonation. Intonation refers to the guitar being in tune regardless of where you play on the neck. As above your local dealer should be able to help. If you would like to know more about this model click here.