I just feel like to design/build something you truly envision for your condo, you need Casino jackpot farming, which based on my experience requires more than 16 hours to get about a million units. This is a good amount of units for you to start designing the condo of your dream, or a condo that's worth others to look at.
Your options are Triple Diamonds (which has awful progressive payout) for the jackpot, or Wheel of Money. At this point, the developers like the odds because they believe people are fine with it. I've sat on Wheel of Money for about 6 days (around 12 hours per day) straight with no jackpot, and while I was asleep someone took the seat and got the jackpot. I tried again for the next 3 days, only to be greeted with an update that forced me to restart. By the time I got there, someone else was on it.
I've seen so many people getting jackpots and quickly disconnecting and quitting the game without any excitement. I've done it twice from TD jackpots. By the time you get it, you're way too exhausted to be excited for anyway.
To design a condo that looks decent, sure play games you might like (personally I think all games in TU feels very clumsy except for the mini-golf, bowling when it's not lagging and LC), but if you truly want to design a condo people might stay longer and socialize, you HAVE to have a lot of money and only by grinding in Casino will get you that in a reasonable amount of time... relatively speaking.
Seats being stolen and way too low odds that forces hundreds hours of spamming space and other keystrokes for anti-bot measures are not fun elements of a videogame. Sure, that might be how "real-life" Casinos work, but this is a videogame supposed to be casual to have fun.
Developers don't like people farming at Casino, and want people to socialize, but refuse to rework the jackpot system and the odds. Instead, they secretly lowered the value of Casino farming (http://forums.pixeltailgames.com/t/0-3-4-3-5-credit-bets-only-add-2-credits-to-the-jackpot/23316/4) and increased the average of payouts which didn't really change much.