what to charge?

I took some interior photos of a friend's house, which he is selling. He wants to post the photos on line to advertise his home. I took about 20 pics, did a little post processing.
In all, I spent about 2 hours on the project. What would be a fair price to charge?

i was thinking around $30.00. There is no printing involved, I emailed the pics to him.

Any advice?

Thanks!

The word "Friend" is used. What price do you put on friendship??