Explanation:

- Option 1: Expensive

- While "expensive" could describe the type of lifestyle he'd lead, it doesn't necessarily convey the idea of comfort or abundance that "luxurious" does.

- Option 2: Conducive

- "Conducive" means making a certain situation or outcome likely or possible. It doesn't relate to the nature of the life being lived in terms of wealth.

- Option 3: Destitute

- "Destitute" means lacking the basic necessities of life, which contradicts being a millionaire.

- Option 4: Luxurious

- "Luxurious" means characterized by opulence, comfort, and wealth. This fits perfectly with the idea of a millionaire's lifestyle.