Renting out primary residence - and rent smaller place - Finances/Tax impact?

Renting out primary residence - and rent smaller place - Finances/Tax impact?
Added (1). With changes in my personal life. My current primary residence is too big and maintenance, higher utilities.
What if I rent out my current house and I rent a different smaller place.1) How does this impact tax deductions for the mortgage interest paid.2) I lived in this house for 2.5 years after buy and decent equity, will I need to pay any capitals gain if I re-classify it rental property. 3) I assume I have to pay taxes on rental income.
I am trying to balance finance and convenience.

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