[shubhamjain]

I agree with the fact that per hour model is not perfect but its really hard to predict the effort that will be involved in the project. I don't think even I can be sure of things I want before commencement of project.

Plus, you may have to deal with client asking trivial changes which I specially find hard to refuse. Is there a model where you can charge more if it exceeds your expected time of completion?

[cazer]

You make some good points. I think the best solution for your scenario would be to make sure you have a detailed Scope of Work going into the project. The SOW lists what exactly the job will entail. If the client's requests exceed the SOW, then you have the right to either refuse to do the item or to renegotiate.