Real estate investor here. You can't claim "lost rent" as an expense. The deduction you're referring to allows you to deduct up to $25k per year of actual renta

Real estate investor here. You can't claim "lost rent" as an expense. The deduction you're referring to allows you to deduct up to $25k per year of actual rental losses against your other income, but only if your income is below $150k / year. In no way is this an incentive to leave your property vacant.