Haunted houses!
Or more precisely, Arthur was planning to purchase a large number of haunted houses!
Since the Countess had exhibited a "Miracle," South Los was about to set off a wave of financial myths, so it was time for Arthur to take action.
He would buy property directly, come up with a plan to build up the block, use that plan as collateral to raise funds from the banks and the wealthy of South Los, or simply raise funds directly from the Countess. Then, with those funds, he would buy even more land quickly. Repeating this cycle several times, with the premise of a large population flocking to South Los, and with just a little instigation of the local South Los natives, the bubble could be inflated rapidly. Arthur was confident that he could rank among the top of South Los's wealth list in the shortest possible time.
Arthur really wanted to do this, but he was quite self-aware.