AWA421 - Did legionaries and auxiliaries have to bribe their way into the Roman army?

The second part of Carlos' question from a few episodes ago: "Second, somewhere in an old issue of AWM I have read (but I cannot find it again) that, to become a legionary, recruits needed to buy their way, and that the required payment (bribe?) was lower if you joined the auxiliaries instead. This was surprising, because I also read about a signing bonus (viaticum) by the second century. The…