In Germany, most Ph.D. students (with university jobs) do exactly this: they are responsible for tutorials, seminars etc., selecting problems, working with the student TAs that actually hold the tutorials. This is all part of their university job. The workload is probably comparable to 4 hours a week workload. (People on actual stipends are not required to do so; some do, some don't.)
As to whether this is a good idea: we can't answer that question. It will depend on your stipend and your expenses, on how badly you need the money, on whether you could have meaningfully used that time to further your research or not (because you can't do full-power research all day long, and you might just as well include some planned lower-power time in your week), on how much quality of life tutoring gives you (or takes away from you) and so forth.