Speaking multiple languages has all kinds of benefits and learning another language can be one of the most rewarding experiences of your life. It can also be incredibly difficult depending on the language you pick.
English speakers start off on the language tree knowing a Germanic language, loosely related to other languages like Dutch, German and Swedish. Romance languages, like French, Spanish and Portuguese, are another branch of the tree, related to each other, but more difficult a starting point for someone who speaks a Germanic language.
This excellent infographic breaks down how long it would take you to learn each of the 9 most common languages in the world, from Spanish to Mandarin Chinese.
Romance languages Spanish and Portuguese rate the easiest, but the difficulty level quickly gets harder as you move into languages like Hindi, Russian and Japanese that all have different writing systems (not the Roman alphabet we use in the west).
You can also find more infographics at Visualistan