“If it’s not profitable, it’s not microlending — it’s charity,” Yunus said on a recent trip to the U.S. The question, then, is whether there is a role for a Third World lender in the world’s largest economy. … The working microfinance equation consists of borrowing funds cheaply and keeping loan defaults and overhead expenses sufficiently low. Microlenders overseas , including Grameen, do that by charging hefty interest rates — as high as 60% or 70%. …