What have you already done? Technically, none of these places are "where you should start."
Even aside from that, do you have any strategy? If for example you were planning to make some contacts at a trade show, perhaps business cards would be a higher priority than any of those things.
Also, a sell sheet or something like it typically will come before a prototype or even a CAD drawing, even where a situation requires one of the two. The whole purpose of that is to make an impression and get a foot in the door. Without a foot in the door the prototype is probably useless, and a prospect might not be impressed by CAD drawings. But then there's the whole issue where, maybe taking care of a prototype first helps you output a better sell sheet as you would be able to take a picture of the prototype...
Also, ultimately, if you have enough money to work with and have a lot invested in your outcome, you might as well go and invest in all three. If you are on a tight budget and have about ten other inventions in the backdrop, why bother with anything but the sell sheet (or something like one, like a short .PPT presentation).
Lastly, not having graphics programs on your computer is nothing more than an excuse. There are free Graphics programs out there (i.e. The Gimp, Irfanview) and PowerPoint alternatives (i.e. Open Office). The reason you choose to outsource a sell sheet (or something like it) is because you lack faith in your design skills and/or you just don't have the time to put something together yourself.
- Billbill@criteriondynamics.comwww.criteriondynamics.com
