The achievement is unlocked when your funds on hand reach 100,000. It will almost certainly be unlocked during normal game play unless one makes a conscious effort not to accumulate funds. It can be unlocked fairly early. Players who want to get it out of the way quickly can go to an item shop and sell the materials they gather. Once the available funds shown on the Item Shop sell screen reach 100,000 the achievement will unlock. If a save is made just prior to going to the item shop, the player can revert to the previous save and recover the sold items back in inventory.
It is not unreasonable to unlock it in chapter 2 if one does not buy anything and does a fair amount of exploring in the desert. My personal rule of thumb is I generally have a little more in inventory than I have gold. So, when I reach 50,000 gold, I am confident that I have enough to sell to get me over the 100,000 mark (this is my 6th time getting Desire without Emotion having gotten the equivalent achievement/trophy four times on the PS4 and once on the PC). At any rate, it is not difficult to get because both gold and items worth gold are extremely plentiful in the game.
Note: This achievement cannot be bought in the secret achievement shop that becomes available after three playthroughs. If one had the 100,000 gold the achievement costs, the 'Desire Without Emotion' Achievement would already have popped.