Calculation of a Concat Forumla

Im struggling to find how to integrate "null" into this formula, or maybe I am just doing it wrong. I am creating a field and wanted to concat 2 fields into it using the formula builder on Enterprise.

Always copy name1_c
If name2_c exists - concat name1_c, name2_c

So the field should always copy name1_c. If name2 exists, add a coma and name2_c. Keeping in mind that name2_c does not always exist and I must have a coma in the output.

Everytime I try this, I fail. Can I get some suggestions on the correct way to calculate this?