People frequently ask me how soon a loved one in Spirit can communicate once they have left the physical world. As a Psychic Medium, I personally have experienced that our loved ones can communicate right away.
I have frequently experienced immediate communication from deceased souls.
I would like to make a very important note that while communication is possible, not every Spirit/Soul on the Other Side is a good communicator or skilled at communicating as soon as they cross over. In my experience as a Psychic-Medium, some souls are better communicators than others. This is because they are older souls that have this knowledge of communicating through a Medium stored within the memory banks of their Soul/Spirit.
It is also important to note that you need to give your deceased loved ones time to adjust to their new reality and new realm of consciousness. It is equally important to allow yourself time to grieve and adjust to the changes in your life when you lose a loved one. You may be in the depths of strong grief and you need time to heal. If you reach out to a Medium too soon, you (as the Sitter) may not be open and receptive to what your loved ones in Spirit want to share.