There aren't necessarily warehouses in the alienage, since it's a residential area, but he might be able to find something smaller than a warehouse but still a little larger and more open than the standard tiny apartment for his purposes. Buying a building would probably be more than the winnings themselves could manage, but if he gets help elsewhere or saves for a while he might be able to pull it off. Alternatively, if he's not also paying for a lease on housing elsewhere, it might be enough to combine the winnings with his excess Inquisition income to rent something for a while before it runs out. And yes, if you want him to start trying to train NPCs or anything similar, please do submit a plot request!