How do you cost application development?

Hi, everyone….

I am trying to get into the world of systems analysis/systems design, but would like to know how to go about costing my projects. I have a potential client who is interested in having me develop an application for her, but I have no idea how to go about giving her a fair price when she asks me how much I would charge.

How do you charge for applications which you design, code, implement and will maintain?