Should I decline a request to tutor a class I will be taking? I am a first semester master's student. A professor has sent me an e-mail with an offer to tutor a bachelor class (this would be a paid job). I do not know him personally but he told me in his e-mail that I was recommended to him by a professor whose class I took this semester. 

Now here is the conflict: I did my bachelor's at a different institution and in my country, it is normal for universities to require students who switched institutions to take 1-2 bachelor classes in the first semesters of their master. Among the classes I am required to take is the very same class the professor offered me to tutor. As a tutor, I would be teaching exercise classes and grading other student's solutions to the problem sets.

Can I decline this offer for the above reason or could it be seen as making excuses? I do want to pursue a career in academia so I am afraid that this could be misunderstood as me not being willing to tutor classes or do work for the deparment in general.
You need to tell the professor. I would suggest that you tell them you want to tutor the class and believe you have the skills and knowledge, but that you are being required to take the class for credit. Then ask if it might be possible for the tutoring to satisfy the requirement.