Ever since Get To Work, my highest Simileons is 500,000 by running an art shop, and my Sim would be selling art pieces for 100% price markup, but I honestly don't know which is better, 50% Price Mark up, or 100%. 50% still have your stuff sell faster.
But yeah, I too wish we could transfer money between households. You can do that with your retail store, but not households :/... At least I don't think. I also don't like using cheats. The only cheats I use it "free household," because $20,000 is too little.