Answer: I would have said about a month or so, assuming the avocado was mature enough when you got it. A slightly warmer temperature (75 - 80, or gentle bottom heat) might help speed things up. Also be sure to keep it in a very bright and sunny spot. The roots usually form first, then the shoot. Fertilizer might burn the tender new roots so I wouldn't recommend that. I'm sorry to have to tell you to still just be a bit patient.
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