Build Recurring Income

Under what conditions would rental income be considered an active trade or business income for determining the business income limitation for section 179 expense? I cannot seem to find any concrete evidence either way on this.

I am planning to transfer the rental income from my house to my wife account for her personal expenses. I will club the rental income in my total income and accordingly paying the tax. Is any interest earned in my wife's account (from the rental income) to be clubbed in my total income?