Taxes and how exactly TRC agents work

I see lots of offers from various agencies for their "support" for acquiring work permits and eventually TRCs. Now my question is: does this process include actual (nominal) employment in some company for any period? If yes, what do they do about taxes and will any tax history of mine be created in Vietnamese tax department?

These are basically under the table offers, and no you wont have to work for a company and pay any tax.