With the adjective mercenary denoting working or acting merely for gain, it is fair to judge Mr. Jaggers, a character that Dickens based upon an unscrupulous lawyer he knew, as such; however, Mr. John Wemmick. the character who uses the phrase "portable property," is more practical than he is mercenary.
That the main motive of Mr. Jaggers is the acquisition of money is demonstrated even in his treatment of others. For instance, after his arrival at the Three Jolly Bargemen where he informs Pip of his "great expectations," and that he will go to London to be tutored, Jaggers turns to Joe and offers him a compensation for the breaking of Pip's apprenticeship. Then, when Pip does arrive in London in Chapter XX, he witnesses Mr. Jaggers's encounters with various types of people who have been waiting to make legal requests of him. With each, Jaggers asks, "Have you paid Wemmick?" or he threatens to let them "slip through his fingers" if they do not pay Wemmick.
In Chapter XXIV, as Wemmick explains the significance of the two death masks that lie on the shelf in Mr. Jaggers's office, Pip asks him about the mourning rings that he wears around his neck, and Wemmick replies,
"I always take 'em. They're curiosities. And they're property. They may not be worth much, but, after all, they're property and portable. It don't signify to you with your brilliant lookout, but as to myself, my guiding-star always is, 'Get hold of portable property'."
Further, in Chapter XXXVI, Pip speaks to Wemmick about helping Herbert begin "a commercial life" by investing money in his friend. But, Wemmick speaks negatively of giving money to a friend because he is in the office of Jaggers.
Invest portable property in a friend?" said Wemmick. "Certainly he should not. Unless he wants to get rid of the friend,--and then it becomes a question how much portable property it may be worth to get rid of him."
"And that," said I, "is your deliberate opinion, Mr. Wemmick?"
"That," he returned, "is my deliberate opinion in this office."
However, when Pip comes to Walworth and takes up his question again, Wemmick agrees to find a banker who can come to Herbert's aid. And, so, he abandons his opinion of saving one's "portable property." Instead, he promises Pip that he will make certain contacts and procure a position for Herbert. This change of opinion at Walworth indicates the true nature of Wemmick which is generous, rather than mercenary.
In another incidence, after Pip visits Miss Havisham and procures money to assist Herbert, he visits the office of Mr. Jaggers in order to explain the recent occurrences. The avaricious Mr. Jaggers is surprised that Pip has not asked something for himself from Miss Havisham, saying,
"I should not have told her No, if I had been you," said Mr Jaggers; "but every man ought to know his own business best."
However, the ever-practical Wemmick looks up and says to Pip "rather reproachfully,"
“Every man's business....is portable property.”
While Wemmick is as coldly business-like as his employer, Mr. Jaggers, he exhibits less of a mercenary and more practical approach to Mr. Jaggers's clients; furthermore, he is very warm and generous in his personal life, much in contrast to Mr. Jaggers who sits in judgment of people at his dinner table.