I was wondering if there is a statute of limitation for this scenario. I once signed up for an MLM in 2003, unfortunately my customer did not pay me and I could not pay it so that debt went to a third party collection agency. That debt was paid in full in 2004. This week I re-signed with that company (MLM) who is now charging me the fee for taking me to Collections. I was never informed of this second debt at the time of collection nor in the years to follow and I have lived at the same address since 2003 with the same phone number, because when I called them about this fee owing, the confirmed all of the information. I was told this fee is charged if person signs again with the company. Is this second debt legal and is there a statute on this type of debt?

More info is needed, what type of MLM, even what is the name of the company, Reserch on their history of complaints may show some things.

But why after trouble before did you go back with them?

What does your written contract state, nothing else.

And no if the debt was settled and paid in full though a collection agency, there is not "cost of debt" or other charges they collect on.

They can charge you a fee, you can decline to pay it or do business with them. This fee is not based on law, it's their policy.