Email Marketing Software

I have been offered two software design projects. One will take about 4 months and the other one about 2-3 months. This includes coding, testing etc.

This I am doing for a friend.

How much should I charge my friend for these two projects. I don`t know how much does a freelance software developer charges. Should I charge per hour or in one lump sum?

What is the market rate? For both projects the cost is going to be different, of course.

Please help. I have to reply to my friend soon.