Answer: $7,000
Explanation: Thomas' gross income for the year was $7,000, which consists of investment income. However his total deductions were $8,000 (consisting of $2,000 interest expense on loan to purchase stock + $6,000 interest on borrowings to purchase land).
His deductions exceed his income by $1,000 ($7,000 income - $8,000 deductions). Thomas is not allowed to deduct so much expenses that it will put him in a negative position. I.e. He is limited to only deducting until his income is $0. Once he starts going below $0, and into negative figures, he needs to cap his deductions at $0 on income.
This means that since there is only $7,000 income available, he can only deduct $7,000 of his expenses for that given year. The remaining $1,000 deductions can be carried forward to the next year where it can then be deducted.