I and several others use Inkscape, it's free and gets the job done well enough. As for models to recolor, there are several in the Downloads section and Bruno (Scissorsandplanes) has hundreds of free models in this thread:
One model per (non-working) day
With Inkscape, you can also remove the existing coloration on most models pretty easily, so you don't always need a blank template. Play around with it and feel free to ask more questions!
Glad to have you aboard
