dnd 5e – How to plant a guild of thieves without being detrimental to the rest of the group

Background: D & D5e with a steam punk flare. My protagonist is a changing rogue (he can take on the role of other people) with a little magic (Arcane Trickster). My deity has asked me to plant a guild of thieves to act as a network of spies that will grow slowly as the protagonist progresses in his adventure.

I have another question in building the world about how to approach this story in an intelligent way. In this question, I would like to focus on how I could do it without being detrimental to the main story, or to others at the table. I want to do this for fun, but I do not undermine the fun that others have.

On page 186-187, the PHB discusses "Entre aventuras"

Between trips to dungeons and battles against ancient evils, adventurers need
time to rest, recover and prepare for your next adventure. Many
adventurers also use this time to perform other tasks, such as working
weapons and armor, conducting research or spending their hard earned gold.

In some cases, the passage of time is something that happens with little
Fanfare or description. When starting a new adventure, the DM could simply
Declares that a certain amount of time has passed and allows you to describe
In general terms, what your character has been doing. At other times, the DM.
you might want to keep track of how much time passes as events beyond
Your perception remains in motion.

While this does not explicitly talk about planting a super cult of the underworld that you will one day use to conquer the world … I think this would be the appropriate place for this activity to not be harmful. What I do not know … is how much time / money should the investment invest in this.

I remember reading about the player housing / clan rooms in one of the official D & D books, but for my life I can not find it in the atmosphere.

How can I do this within the rules of D & D5e without being detrimental to the existing game?