Like the Prioress and the Monk, the Friar is a not-so-pious religious figure. But his sins are all the more reprehensible because friars, more than any other religious group, were pledged to a life of poverty. In medieval England, friars could be "licensed" both to beg in particular regions, and to earn money by hearing confessions or administering the sacraments. Since friars were not supposed to own property, these licenses were their only means of supporting themselves. But this situation led to rivalry between friars, who could travel from place to place soliciting donations, and the religious figures like parish priests who also depended upon their communities for donations. It was probably because of this rivalry that a particularly strong "anticlericalism," or collection of stereotypes about religious figures, grew up around friars. It is from this collection of stereotypes that the portrait of the Friar draws.
One of the stereotypes about friars was that they traveled around seducing women, and we see this in the Friar's portrait in spades: we learn that he has "maad many a mariage / of yonge wommen at his owene cost" (General Prologue 212 – 213). The Friar probably does not pay for these women's dowries out of the goodness of his heart; we are likely meant to understand that he must marry off these women to pay for the virginity he has taken from them. Moreover, the Friar keeps his pockets full of baubles (pins and pocket-knives) to give away to young wives and earn their favor.
Another stereotype about friars was that they were so crafty at soliciting donations that they could convince a widow to give away her last penny, and, moreover, that they earned far more than they needed, enabling them to live a life of luxury. This is true of our Friar: though a widow might be shoeless, he can convince her to give him money. We also learn that the more money a penitent donates, the easier the penance the friar gives; basically, he is selling the Church's forgiveness. All of these unsavory practices enable him wear a double-lined (and thus doubly expensive), brand-spanking new robe, and to bribe an official into allowing him sole begging rights in his territory, further increasing his earnings.
Like the Monk and the Prioress, the Friar's extracurricular activities are inappropriate for one of his profession: we learn that he likes to hang out with wealthy landowners, barmaids, noblewomen, and tavern owners. Were he truly living the life that St Francis, the first friar, prescribed, he would spend time with the poor and sick. But the Friar says he sees no reason for someone of his station to hang out with poor people – after all, where's the money in that? And finally, we learn that the Friar excels at singing competitions and debate, resolving disputes at "love days" or court days. We know that this is no proper occupation for a Friar because the narrator tells us so: in this, says Chaucer, he is not like a poor scholar friar, but more like a master or a pope. And judging from his portrait, that's probably exactly how this friar would like to be perceived.