I know 1 'Cheat'
Have 3 or less houses
Build the Japanese House (cost 31.000 or less)
If it's build, sell everything in the house, including windows and plants
Then sell the rooms
If you have done that, you may have 30,000 a 40.000 simdollars profit.
Destroy the house completely and build a japanese house again!
You can do this as much as you want.
Only do this with 3 or less houses, or else the Japanese house is too expensive
Good luck!
(Sorry for my bad English)