House buying..??

Not sure where to post or ask but we are planning on buying a house in the next four months and was wondering the process or do we apply months before?? Its going to be our first house our apartment lease ends in four months so we’ll need a place to go and our 2nd baby is also due in four months so yay for stress we arent planning on barely applying right at four months but what would be the ideal time to apply in order to be moving in this time frame??