We are retired and our daughter is thinking of moving to Australia with our grandson to work, will we be able to buy a house to live there to help look after the child?

If your daughter is going on nonimmigrant work visa, you can visit them on visitor's visa which will allow you to stay for a couple of months only.

My daughter is looking to stay in Australia permanently and hoping to obtain a immigrant work visa , would we be allowed to
Go with her.

Not so fast... you may have to wait until she becomes Australian citizen, then she can file immigrant visa for you.