To unlock the "Keep it Clean" achievement, start by depositing a larger amount of money—around $1,500—into the ATM. This will trigger a dialogue prompting you to contact the Laundry Man.
After Dany Steak reaches out and explains the laundering system, access your bank account in the game by clicking the "Login to bank account >>" button. You’ll then see an option to purchase your first upgrade for $700. Once you buy this upgrade, the achievement will unlock.