If you want a plausible explanation as to why the Guild don't object to your character going into the Vaults area, you could always 'bribe' Delvin by paying one session of sneak training.

Assuming your character is smart, and knows enough to know that the Guild might be able to help, they can probably also find out where the Guild hang out. There are basically two ways around this, one: metagame. You see, the conversation with Brynjolf, and I quote, '.I exited the conversation until sufficient information was achieved > Brynjolf walks up to me and starts a conversation >.' is the one I want to prevent from happening. This is the one I want to stay away from that's why I don't want to start a conversation with Brynjolf after finishing the A Chance Agreement.ДЄ Cornered Rat starts > I locate and talk to Brynjolf for information about Esbern > Brnyjolf tells me to steal something in exchange for the info > A Chance Agreement starts > I finished the quest > Taking Care of Business starts > I ignored it for the sake of not joining the guild > I proceeded with A Cornered Rat > quest told me to go find Vekel > I spoke to Vekel and bribed him out on Esbern's location > I exited the conversation until sufficient information was achieved > Brynjolf walks up to me and starts a conversation > conversation lead to expand Taking Care of Business wherein it asks me to collect three debts > ? Not even an option on asking if I would like to do it or not. None, as Brynjolf talks to me about getting the three debts, there's no other option but to proceed to it and start it anyway. Originally posted by Theo Hardmeier:There is a high level persuasion check to avoid the quest if I remember right. Is there a way to stay away from Brynjolf? I tried walking away immediately away from Vekel as soon as I got the quest marker on Esbern but I am worried that the Taking Care of Business might bug out on me considering I didn't talk to Brynjolf yet (and I guess the game wants me to since Brynjolf is the one that starts the conversation, not you, so that means that you need to accept and finish the conversation right? I am affraid not doing so can alter the script). After speaking to Vekel about Esbern's location, Brynjolf immediately speaks to me expanding on the Guild's quest, 'Taking Care of Business'.

Part of the main story line is to locate Esbern, and in order to locate him I need to talk to Vekel. I know, I can choose not to join the guild (and I really don't want to, for the sake of role-playing, sorry if you find me weird) but there is this thing that bothers me. I have two characters who already joined the guild and I noticed that most of its quests require a lot of sneaking and since I have low sneak level, I may have a hard time progressing through the guild. I do not intend to spend any of my perks on any of the Thief skills. You see, I made a mage-type character who focuses on destruction magic and enchanting.

How to join the mages guild in skyrim