Being "experts," as my wife and I are, on detective programs of the 1930's, '40's and '50's, we know that one thing that private eyes could do that regular policemen could not do was to pay for information. Private dicks were always slipping someone $5 or $20, or maybe more, to get the information they needed.
So just exactly how much would that have been in today's money? According to the DollarTimes calculator, $50 in 1940 would have been worth $86 today. So, $20 accordingly would have been worth $345 today. Folks in down-and-out circumstances might well have talked for those amounts of money.