Need help with determining probability for zoning issue

Hi all - I hope I am posting this in the correct forum.

I am in the midst of public hearings regarding some zoning regulations in my town.

Here is my dilemma: I am in need of determing what the probability of a family of 8 (two parents, six children) moving into the same house in my town, every 15 months (a new family of eight every 15 months, into the exact same house, that is).

If a period of time is needed for the calculation, assume 5 years.

I realize this likely will be an astronomically high probability, but it is important to determine nonetheless, and I have no clue how to even begin. Is more information required? If so, what? If not - what's the answer, and how does one arrive AT that answer?

Thank you in advance for your help in this matter.
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