The Thieves Guild is a secretive organization, and they don't let just anyone into their hidden headquarters in Riften. That's why players must start out their quest line by proving their worth in the Riften market, and then by finding the Ragged Flagon underneath the city. Only then will players actually meet the thieves in The Elder Scrolls 5: Skyrim.
However, even at this point players must prove their worth to Brynjolf and the other thieves. The name of this final hurdle is "Taking Care of Business," and it's the last step players must take to fully unlock the Thieves Guild of Skyrim and all the useful benefits they provide.
Extorting for Fun and Profit
To start the quest, find Brynjolf in the Ragged Flagon and speak to him. He wants the Dragonborn to extort three business owners in Riften and get the protection money they owe the Guild. He says the message is more important than the gold, but keep in mind that this quest won't end until players have both sent a message to each target and paid Brynjolf 300 gold.
Players have three ways to approach each target. First, Brynjolf has a suggestion the player can enact to threaten the target. Second, players can start an unarmed brawl with the target, and if they win the target will pay up. This brawl doesn't count as a fight, and other characters won't join in unless players hit them. Third, players can kill the target. Players won't get any money from a dead target, and there's a good chance someone will see the crime and report it to the guards, but this still counts as completing the objective.
One last thing to keep in mind is that the last target will always give up without a fight. Players can visit the targets in any order, and whomever they reach last will have heard about the other two and will give up the money immediately. This happens no matter how player deal with the first two targets.
Keerava
Keerava is the proprietor of the Bee and Barb Inn. Brynjolf suggests talking to Talen-Jei, another Argonian in the inn, and this is the easiest way to get Keerava's money. Speak to Talen-Jei about Keerava, then ask Keerava about her debt. Choose the only options available and she'll pay the 100 gold.
Bersi
Bersi owns the Pawned Prawn, the general store of Riften. According to Brynjolf, he really values his ancient dwarven urn, which sits on the table across from his counter. Attack it a few times with any weapon until it breaks, then collect Bersi's payment.
Haelga
Haelga runs Haelga's Bunkhouse, which isn't a business players can interact with. She's a devout follower of Dibella, so turn right from the counter and then turn right again to find her statue of the goddess. Steal it, but try to avoid being spotted since doing so is a crime. With the statue in hand, players can threaten to throw it away to get Haelga to pay.
Once players have dealt with the three targets, return to the Ragged Flagon and report to Brynjolf. Brynjolf will be angry with the Dragonborn if any of the targets died (even if it happened before and wasn't the player's fault), but no matter what he'll make players a full member of the Thieves Guild. This comes with a special set of light armor, access to a shortcut in the Riften cemetery, access to every Thieves Guild fence (although there's only one at first), and access to the radiant Thieves Guild quests that will eventually unlock more cities and resources.
The Elder Scrolls 5: Skyrim is available now on PC, PS3, PS4, PS5, Switch, Xbox 360, Xbox One, and Xbox Series X/S.