This puzzle gives four people, four professions and four salaries, and asks specifically for the lawyer's starting pay. Since Biswajeet is named as the lawyer, the real target is Biswajeet's salary.
Working through the four salary values by elimination leaves exactly one figure open for Biswajeet, Rs 60,000. This also satisfies Arvind earned more than Biswajeet, since Arvind's Rs 70,000 exceeds it.
Let's summarize:
So the lawyer, Biswajeet, started on Rs 60,000.