I did both hourly and project based pricing models when consulting. Each have pros and cons but for projects that aren't "off the shelve" and do require discovery days, lots of inputs from client and a level of solution design from the consultant, the key thing is milestones. This way you can fend off scope creep and also be very specific on deliverables.I.e.:created x feature: 10 hours( 15% of the overall project). As for the rates, one hits the ceiling pretty quickly with hourly rates: try pitching $500/h if you not a lawyer. That's why value based pricing is the only way to push it up as high as possible. It's one thing to say that you'll be charging $200/h for the next few weeks and another when you say you'd build something for $24K that'll make the company $500K over next 12months.