"Once you have finished your founder, move them into any empty lot. Return to the world screen. Select your founder on their empty lot and pick “Move Family”. Locate a residential 50×50 lot and bulldoze it, evicting the family present if there is one. The lot should now cost exactly $10,000. If it does not, it is not an eligible lot.
Move your founder into the new empty $10,000 lot. This will leave them with $10,000 in cash. Before doing anything else, purchase the Knight of the Octagon Table decoration costing $8,200 and place it in your family inventory. It must remain there for the entire challenge. Think of it as a sort of price of a nobility title; a right to call yourself a Legacy family. Once this is completed, you must ponder what your family’s succession law will be."
To start the legacy challenge, you only have $1,800 to begin with...you start with your $20,000...then buy a $10,000 lot, then purchase a decoration for $8,200 - this effectively reduces your funds to $1,800...not a lot LOL I started with a bed, toilet and fridge. I have managed to add a kids room, bedroom and bathroom to main living area as Gen 2 is almost an adult.
****I also have to say, sims can get much more unhealthy by not working out in this game. I have a very chubby sim family right now :)