is it acceptable to fellow monks to offer to pay for help

If you mean by that to get a monk to answer a question on Perl Monks for you, then I'd say "no." The whole point of this online community is for it to be a resource for the Perl community at large. Part of that being a resource means the free exchange of information in the form of help, questions answered, impacts of feet on someone's gluteous maximus or whatever is needed (or desired.)

I'm not even sure the gods would be amiable to having folks advertise looking for professional services. We try and avoid spam around here and commercial advertising of any sort would be highly frowned up.

If, however, in the course of a private conversation either through the message facility or an offline conversation you and a monk here agreed to some sort of contract involving the exchange of money/barter/favors/trinkets/whatever then what goes on between consenting adults is of no concern of the Monastery.