As soon as you start lifting weights with the goal of building muscle, you're on track to becoming a bodybuilder. But it will take some time before your gains are noticeable. You can expect large gains as a novice but eventually your muscle growth will begin to slow.
A novice adult lifting weights three hours per week can expect to gain four to 15 pounds per year without the use of steroids or hormones. After two years of lifting this person should expect just three to 10 pounds of annual gains. After five years this growth will slow to about two to seven pounds per year. After lifting for 10 years this person can only expect to naturally gain up to two pounds annually.
If you lift more often you can expect bigger gains. If you lift for seven hours per week you can expect to gain eight to 20 pounds annually. After two years this will slow to five to 15 pounds. After five years you can expect to gain three to 10 pounds and after 10 years you can expect between one and four pounds of annual gains.