I was offered a job testing iPhone applications - Germany

So, I already have a full-time job in an IT consulting company in Munich. I work with a guy who owns his own company and writes Iphone applications on the side. He needs me to test out his new application in English and he wants to know how much I will charge him to do it.

I'm estimating that this app will take 15 - 20 hours to test. I have no idea if I should charge him by the hour or by the project.

Does anyone have any suggestions? One of my other colleagues said "50€/hr" but I have no idea.

Thanks in advance for suggestions.

€50 an hour sounds about right to me for an established company, but if he is just a bloke on his own I think a little less, say €35 - €40 would be better.

Depends on the person, is he a registered businessman or is it just an under the counter job between friends.

If a real business then Charge him by project, you just need to work out how long you going to spend on it. workpackage based work is always better.

Be aware if it's a real business arrangement you will pay tax and probably should be registered with the taxman as a freelancer.

I would recommend by the hour, that's less risky for you. The testing may take much longer than you think.
50EUR sounds ok. Will you pay tax or is it friendly schwarz? In either case, make sure you get some payment in advance or something signed between you two. In the past I matched two friends, one looking for a translator for an online application, the other the translator. At the end with the online application it didn't work out, no payments. I ended up paying the translator friend.

I prefer the "friendly scharz" myself - otherwise I will have to become an employee of his because I cannot freelance on my Niederlassungserlaubnis.

I was thinking more in the 35-40€ per hour range. I estimated about 15 hours of testing for him. Let's see what he says. I read through the testing script last night and his translator didn't do a very good job. So, I will correct all that as part of the testing.

Thanks for the info.

15% of the gross when he sells the app?

In the end, I went lower than I would have liked to go but, it was the first time I did it for him. He asked me if I wanted to translate the next app that he writes. For that, I can charge more. It's a fun little thing to do on the side for some pocket money.