Earn your first million Euros.If your currency is not set to Euros you may have to earn more/less than 1 million to get this Achievement. You can change the currency in the settings (Settings > "General").
It would be better to do this achievement after finishing the game (sell all houses once).
Easy way to get the Achievement:Buy the "House that is hiding something".
Go to the house, go downstairs and break the wall on the left, next to the junction box. Sell everything in the secret room (armchair, sideboard and the valuable painting). Sell the house afterwards. You will make a profit of $60.000 - $65.000 in less than 2 minutes. Repeat everything until you have enough money.
Source/Credit:
https://steamcommunity.com/app/613100/discussions/0/16386615...