Buying a banjo seems like it should be straightforward, but there are several different types of banjos available, such as four-string, five-string and six-string banjos. There also are 17- or 19-fret banjos. The sizes also vary greatly. Buying a banjo will require some thought about the type of music desired, how large the banjo should be and the skill level of the person playing.
A five-string banjo is traditionally used in bluegrass and finger-picking styles, which require more skill than some other types of styles. Four-string banjos are most often used in music that requires strumming, such as Dixieland-style jazz. A six-string banjo is basically a guitar in the traditional banjo shape. For people who want to learn to play a certain style, looking at banjos designed for that style is going to be the best bet. A person who can already play the guitar might enjoy the feel of the six-string banjo because it's almost identical to the guitar.
When buying a banjo, one will have to choose between an open-back banjo or a resonator banjo. Inexperienced players typically go straight for the resonator banjo because of its appearance. Traditional bluegrass banjos are open-backed. The open back simply doesn't have anything attached to the back portion of the instrument. This creates a mellow tone. These are also lighter than resonator banjos, so they are great for beginners.
Choosing between these styles is mostly a matter of style preference. It's best, however, to choose a resonator that has a detachable back if the resonator banjo is the preferred choice. This way, the player has the option to experiment with the banjo both ways.
Although price will be a concern for most people, it should not be the deciding factor. The cheapest banjo might not be the best, and buying the most expensive might not ensure the best quality. Instead, look at the price and compare the features with several others. Don't be afraid to pick up the banjo and hold it as though it is about to be played. Strumming and moving between frets should be easy and natural.
The hands should be able to maneuver around the frets without much discomfort. If any chords or strumming patterns are already known, the banjo should be played prior to purchase. This lets the player get a feel for the overall sound. A cheap-sounding banjo won't be played as much as one with great sound. Buying a banjo without playing it first could be a mistake.