I want to make an 8 inch cake thats 4 inches tall

how long does it have to be chilled before frosting and fondant? how far in advance can I make the cake?

thanks!

After assembling the cake, I'll put on a crumb coat on it and let it sit at room temp overnight.  This allows the cake to settle and for any irregularities to appear. 

I clean up those irregularities and then put the cake in the fridge for maybe an hour.  This allows just the outside to firm up, but not for the cake to get so cold that it causes the cake to sweat.  After I apply the finish coat of buttercream, I put the cake back in the fridge for another 30 mins.   I roll out the fondant, take the cake out, and cover it--again, little to no sweating that way.