Ok so this achievement is pretty time consuming. A standard game of monopoly has 12 hotels and will require $6,200 in order to buy out all of the hotels from the bank.
The easiest way to get this achievement is to play the game with 3 other controllers that you are playing. While its possible to get this achievement just by playing a game so many different factors have to line up including the most important one, not going bankrupt before the 12 hotels are built. So what you should just do is play the game with 4 players which u control. This will make it so there is $6,000 on the board at the beginning of a game. Then just go around buying up all the properties until between the 4 players you have all of the brown, cyan, pink, orange, and red properties. Once u have all those properties just trade them all to player 1 along with each players cash (make sure player 1 has a property to trade each of the other players such as a R.R.) and then upgrade all of your new properties to hotels. Ding achievement unlocked!