Boston:

Another initiative, presented by the late Mayor Thomas Menino, is the Renew Boston Whole Building Incentive, which reduces the cost of living in buildings that are deemed energy efficient. This, much like the green housing developments, gives people of low socioeconomic status an opportunity to find housing in communities that support the environment. The ultimate goal of this initiative is to enlist 500 Bostonians to participate in a free, in-home energy assessment.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". The goal is to get how  many residents to sign up?
500