To unlock the Ledger inRDR2, you need to go to the Contribution/Donation box in your camp (Horseshoe Overlook, The Hearthlands, NH) and Give all the Debts. After, you can find the ledger to the right of the contribution box at Dutch’s tent....
Money is a very important thing in every open world game. There is a multitude ways of getting it. This page shows all legal ways of getting money. Moreover, we show how to make money in RDR2 and what to spend hard-earned cash on.
It's hard not to be poor in the earlier chapters, though things get a little better later when you unlock (ha, ha) the Red Dead Redemption 2 fence locations and lock breaker to trade your collected trinkets for actual cash, but even after then it's worth knowing some good money making...