From Hari-bhakti-vilasa:
atmano nicalokanam sevanam vrttisiddhaye
nitaram nindyate sadbhirvaisnavasya visesatah ||9.256||
"For livelihood, the service of lower grade persons is blameworthy (nindaniya) for a respectable man. This is especially so for Vaisnavas."
Digdarsini tika for the above verse:
atmanah sakasat ye nica lokastesam, vaisnavasya tu nicalokasevanam
visesato'dhikam nindyate, nicasevanena
nicanam-avaisnavadustajananam-
"Lower means in comparison to one's position; especially for Vaisnavas to serve lower grade persons is especially blameworthy. Serving lower grade persons in this case means (adhinatva) taking orders of or being dependent on one who is not a devotee and so is a rascal (dusta) because this engenders great fault."