Useful life of the dwelling. "Useful life of the dwelling" shall mean the period of time, as determined by the Dept., that the multiple dwelling is expected to be habitable at a level of comfort, safety and sanitation compatible with current requirements of state and city statutes, ordinances and administrative regulations, where there is regular maintenance and care of the major building systems by competent mechanics.
Useful life of the rehabilitation or improvement. "Useful life of the rehabilitation or improvement" shall mean the period of time as determined by the Department that the improvement is expected to function in good condition, with routine maintenance and repair.