Vaishnava Samhita. Gopinatha Charitam. Vol II Book VI Chp 6 Shloka 15

जन्मान्तरकृतैः पुण्यैरणेकैर्भाग्यशालिभिः |   
एवं सद्गुणसंपूर्णो लभ्यते वैष्णवो गुरुः   ||

Such a guru, a true vaishnava endowed with noble qualities is obtained only by those fortunate ones who have amassed merits in many births