What lenders require
Some loans require documented reserves, measured in months of the housing payment. Investment properties and multi unit purchases usually require the most, and primary residences with strong files sometimes require none.
Meeting the requirement is the floor, not the plan.
What life requires
The first year of ownership has a predictable rhythm of unpredictable expenses. A water heater, a tree limb, a dishwasher, a set of blinds for windows you did not measure.
Buyers who keep a cushion describe their first year as fun. Buyers who spend to the last dollar describe it as tense. The house is the same house.