Final answer:
Joseph can deduct $10,000 of the rental loss.
Step-by-step explanation:
Joseph can deduct $10,000 of the rental loss. The deduction for rental losses is subject to certain limitations. If the taxpayer actively participates in managing the rental property and has an adjusted gross income (AGI) of less than $100,000, they can deduct up to $25,000 in rental losses. However, the deduction gradually phases out when the AGI is between $100,000 and $150,000.