A more specific, albeit less chummy, answer:
1. Around 40-50 people get public interest grants of $3,500 for the summer, which isn't alot but is enough to pay the rent.
2. There is also are a sizable block of people who work for professors, at around $7/hour.
3. Other options include working part-time in the legal arena and then finding another job to supplement your income.
4. And, some people don't have a legally related job at all.
5. But, although it's rare, it's not unheard of for someone to have a paying legal job after their first year.
Incidentally, you can make a good deal of money waiting tables. When I first moved to Boston, before I started law school, I was making $50/night on weekdays and $100/night on Thursday, Friday, and Saturday at a relatively inexpensive tapas bar.
It's true that Boston isn't cheap, but you can make your way there. After all, lots and lots of people do.