How to build personal credibility

Me and one of my fellow liked an idea. He said if I need investment for that start up, I will be happy to make. But that was more like a coffee table discussion which lasted for an hour. I think I need some personal credibility to convince him to join me on it as a partner.

The guy is in job and earns a lot. I am a just out of college entrepreneur so I think I need some personal credibility to get his trust. What things I should keep in mind when I will ask him seriously to join me so that I look credible?

Sell your business. Cover all aspects and show him a projection.

My professor once told me that, you can get anyone to join you as long as you can convince them. Make him believe in your project. But first, you must believe in your project.

Start building on your Idea.
make a power point presentation with features explained in brief.

Make a spreadsheet outlining the expense required
it should also include sales projections and what kind of return of investment you are looking forward to.

If your "mentor" is already in a job and owns a lot he may simply want to invest a small sum on your idea if he hasn't got much to loose and knows what he is looking forward to in terms of profits you can share with him.

Well, expand idea of 'selling the project'. 'sell yourself' using that project as an example, and I would say show him future ideas, that goes pass the boundaries of that project so he can see that you are not limited to that specific idea, but rather to see that you can think.