Often people who are interested in learning the banjo but haven't taken the plunge yet ask me, "Is the banjo hard to learn?" The answer is a definitive "No". The banjo is one of the easiest instruments to get started playing.
Before going further, we must understand that there are different types of banjos, and a number of different styles of playing and traditional genres played on each different type. There are 4 string banjos, 5 string banjos, 6 string banjos, banjo ukuleles, and so on. But 99.9 percent of the time when someone tells me they want to play "banjo", and they don't give me any other information, they are talking about playing the 5-string banjo. This is by far the most popular type of banjo. So for the rest of this article when we talk about playing "banjo", we will be talking about playing the 5-string banjo.
The 5-string banjo is tuned in what we call an open tuning. It is an open G tuning, which means if we strum all of the strings without fretting any of the strings, we will be playing a G chord. Because of this fact, it is possible to start strumming a 5-string banjo and playing tunes in about 5 minutes, even if you have never played any instrument before. I know this is a fact because through the years I have taught thousands of people at music festivals how to play a few tunes such as "You Are My Sunshine" in less than 5 minutes.
Here is a great video that goes through this method of playing.
You say "sure you can teach me to strum some chords, but I want to play like Earl Scruggs". Well this statement is a little ridiculous because Earl Scruggs was one of the best American musicians of all time and is probably the most influential 5 string banjo player. To achieve mastery of any instrument at the level that Earl Scruggs did is going to take a lot of dedication. But, you can easily learn to play in the style of Earl Scruggs, which is the 3 finger bluegrass style. This style consists of a series a roll patterns that you can easily learn and play over some chord shapes.
The other main style of 5-string banjo is the clawhammer style. In this style you usually don't use picks on your fingers, and is a downward picking/strumming style that is traditionally used to play old time Appalachian string band music and folk music. Once you are confident in playing the basic clawhammer picking pattern that is often called the "bump ditty" pattern, you can go forward and start playing a lot of tunes in this style. Here is a great video to get you started playing this style.
To sum up, don't be intimidated by the banjo. It is definitely one of the easiest instruments to get started playing. The strings have a light gauge that are easy to fret. The neck is thinner that a guitar or bass so it is easier to play. And the open tuning makes playing your first chords a breeze. So, don't put it off. Play the banjo today!