There are a lot of people here who make amazing models with Pepakura designer. I think you could get a lot o help here with that. I used Rhno3D 4.0. It is very costly. I do a lot of computer aided design, so I have oher uses from this ind of program. I also use Adobe Photoshop CS3, and CS5.
That being said, there are people who make fantastic models using Paint! Some use Blender, some use Sketchup. You will have to find a program that feels intuitive that feels intuitive to you. So you may find yourself starting with one program, then moving to another. Many people look t how designs they like are made, and use that method for their models. There is absolutely nothing wrong with this. It is in fact why so many models seem to go together the same way.
Figure out how much money you want to spend. No body I have ever met makes money off of modeling. Some make some small change, but not a living. There are so many free models, frankly, I think you would have to have something rather special to charge for it. There are quite a few models that fall into that category though. I have purchased a few models.
Also, if you find a model that you even have the slightest inkling you may want to build, download it! Models have a way of disappearing.
Try the following sites, all their models are free, and there are more than one could probably do in a lifetime!:
Paper-Replika
http://paper-replika.com/
Paragon Models:
http://www.freewebs.com/paragon19/
Jaybats Models:
http://www.freewebs.com/jaybats/
Hello all. I'm new to the paper model scene. Been building plastic kits off and on for years. But thought I'd try my hand at paper modeling after viewing some of the interesting ones on the web so thought I my get some advice by joining the forums. Have tried my hand on a couple of simple designes using paper, tape and glue. Looking forward to trying cardstock but will need some more experiance before I start anything complex. 
