Can I get temporary custody of my grandson until my son can get on his own 2 feet

Who has custody now? Why do you want it? How old is grandson?

Also we need to know where in the world you are located as the laws vary from State to State.

Maybe. But we need a lot more background to be able to give you a reasonable answer. Where is the mother? Why does your son have custody? What does get on his feet mean? Where are you located. And much more.