Unable to show actual income

My friend is an Autorickshaw driver. His monthly turnover is around Rs 15,000 (Rs. 1,80,000/p.a). He spends Rs 3,000 for gas so his earnings are around Rs. 12,000 per month or Rs. 1,44,000/p.a. He wants to show this income but has been advised against it. Last time when he filed his returns the turnover was shown as 180000 and his profit/earnings as 40,000. He was told that if he wants to show 144000 as profit than he has to show turnover more than 2.5 lacs which would be false income and would not be able to prove the source and expense. On my advice he deposits the cash earned in bank account and pays for gas by debit card. His main reason to file returns is to be eligible for applying for loan. At this amount of income he doesn't qualify for higher loan amount. Please advise.