Estimating piano tuners in a university town

Estimate how many piano tuners work in a university city of about $120{,}000$ people.

Around 3 to 5. Say $50{,}000$ households with $1$ in $20$ owning a piano, plus colleges, schools and churches: about $3{,}500$ pianos, each tuned about once a year. A tuner doing $4$ a day for $250$ days handles about $1{,}000$ a year, giving three or four tuners. Explain each assumption and give a range.