I know that people work it different ways -- whether you're "eligible" for any employer's 1L program is up to them, of course, and in this economy it's almost all volunteer work unless you're super snowflake.
Ideally (for my money), if you are in a four year program, get some legal work experience if at all possible and go for a summer associate program the summer before you're going to graduate (the 3e summer, which at GULC for example is recruited for alongside the 2L summer).