Thanks for the chapter!
He should definitely check the book for fine print. Especially after that comment where she's 100% successful negotiating except for when she fails. Sure there's benefits once you hit rank B but are there additional responsibilities? Usually in guilds when one hits Rank B at the least it means they're considered potential fighting strength and the kingdom or guild can force them to take certain requests. Varies on whether or not if there are (un)favorable conditions, "adequate" compensation, etc. or being that rank means they can tell an adventurer to do this and that like it or not for a pittance while claiming any materials or gains and can severely punish the adventurer with jail, exile from guild, unpayable fines, or whatever floats their boat if the adventurer refuses. Usually this isn't abused to avoid dissuading adventurers from ranking up or moving elsewhere but there's always a government official looking to make a profit on someone else's efforts and abusing their position. Forced requests could be subjugating a high ranked monster nobody wants to get near, defending the city from a monster stampede (what happens when a really large number of monsters suddenly appear and rush in same direction, usually towards a city,) or other jobs which require a high rank and skill to do and survive.
In any case, considering Iris is on the cover I'd say she's going to get along well with MC or at least interact with him a lot. Toss up whether form a party or not though, could just end up running into each other a lot. So does her name mean she's part newt and part dwarf cursed into a dragon form?