"The sort of business which pays the bills," he replies dismissively. In other words, professional courtesy prevents him from discussing it - and money is the sole reason he works there. "Unfortunately, my situation does not allow for me to be selective in my choice of work. Hellsing was an immediate opportunity."

And he saw that Lucius and Narcissa worked there and thus assumed it would be an acceptable measure, but that goes unsaid. This Lucius can figure it out for himself - and, too, that the invitation to meet at Hellsing was down to the assumption mutual employment rather than a cackhanded trap.