Here's a cool cheat I use that works every time for getting loads of Simoleons.
1) Make your Sims plant are bake something that results in a lot of Simoleons(like the beans or something)
2) Exit the app and double click the home button
3) Press and hold the Sims Freeplay app and little red minuses appear, press the Sims' FP minus(it Doens't delete the app)
4) Go to Setting and change the date one year ahead in our case 2013
5) Open up the Sims Freeplay app
6) Your Sims should be done planting or baking!
I hope this works for you, it does for me and now I rarely come across an item I can't pay for! Good luck!