Why does Jean rent the house in the Rue Plumet?

Valjean has rented a little house in the suburb of Saint Germain, which is distinguished by its secret exit (constructed by a judge who wished to visit his mistress). Why did they leave the safe haven of the Petit-Picpus convent? Jean Valjean wanted Cosette to live a normal life, one not constrained by the rules of the convent. After the death of Fauchelevent, Valjean told the nuns that he had inherited a small sum from his brother and departed the convent with Cosette. Actually, Valjean has rented two apartments in Paris as a precaution; Cosette and a female servant named Toussaint live in one on the Rue Plumet.