Who is Pip's guardian in Great Expectations, and why does he/she set Pip up to room with Herbert?

Pip's guardian is a lawyer named Mr. Jaggers.  When Mr. Jaggers unexpectedly shows up at Joe's house and delivers the news that Pip has a mysterious benefactor who is going to pay for Pip to become a gentleman, Pip and others assume that Miss Havisham is the anonymous sponsor because Jaggers is her personal lawyer.

When Pip arrives in London, he goes to Mr. Jaggers for almost everything since Jaggers is in charge of his finances.  The lawyer arranges for Pip to room with Herbert Pocket (a relative of Miss Havisham) because Herbert's father will train Pip in etiquette and because Herbert is acquainted with many of London's customs. He has been in the city for a while and works at an insurance agency of sorts, but he, too, has ambitions.  He wants to get into trade at some point or have his own fleet of ships (instead of working for a company which insures them) to trade with.