The Sims Freeplay

This achievement requires that you save up 50,000 Simoleons. The must be in your possession at one time. It is not cumulative. This will come with natural progression most likely, once you level up and have a good amount of Sims. You may as well wait for this if you can, as on your way to 30,000,000 simoleons, you should have way more than 50k in your bank at some point. The achievement will pop when your account surpasses 50,000.