Start Avocado in Existing Pot

I took the pit right from the avocado and planted it with my tropical plant. It is flourishing so far. I guess I need to mist it. I will stake it up if it seems to lean but so far it hasn't. I heard you needed sand in the soil. It doesn't have sand in it but I might add that later. I am thrilled that this even came up and is doing good. There was already fertilizer in the soil when I planted the avocado seed.