After my Bettas have mated, how long will it take till the female lays her eggs?

She lay's her eggs when they mate :) I suggest that you read all you can before your decide to go ahead with breeding these fish. And not until you understand what is required and you think your up to the job.

when the male betta wraps around the female to get the eggs out, they fall to the bottom and the male goes and picks up one at a time to put in the bubble his nest till all are in hthe nest. the female has to be taken out or she will eat the eggs and/ or young. the male then fertilizes the eggs in the bubble nest and babysits. when the eggs hatch he tries to keep up by making a fresh bubble nest and shoot the fryes back in the nest (no the male wont eat the frye.., yet) this is when you know the male needs to be taken out when the babies wont stay in their bubble nest. whatching the male trying to put the frye back in a bubble nest is halarious. my dad use to raise bettas and sell them to an aquarium up in Macidonia, Ohio, so I have a little know of bettas.