The boundary has to be consistent before the 38-day figure means much. A handful of units on a busier street, or just beyond the preferred area, could change the result when the sample is small.
I would map both neighbourhoods first, then classify each unit as genuinely new, continuously...
The rent approach needs more detail. Is the apartment vacant or currently let, what is the monthly rent, and what is included? Using eleven months can represent a vacancy allowance, but it does not resolve whether service charges, non-recoverable costs or the current lease terms weaken the...