Hi Exemplaris,
Qwerty is right - you don't need qRules. Just wrap your controls in a section that has a formatting rule that hides the section if the one value is not selected. You can add default data to the form so that the section always has fields in it. Of course, you can't require that they be entered since that would cause a validation error. But, so long as the fields aren't required, having them blank should not be a big problem.
qRules price tag? Is today Monday or what? This forum is free dude. We pretty much give qRules away. We certainly don't make any money off of this forum and qRules is so far from being profitable that it's currently yet another gift to the community. We charge for it because most people end up needing an hour or two of support and if we gave that away for free too we would go out of business. OK, so you have no money. Fine. You can have qRules for free and the cost of a 4-5 sentence testimonial describing how it solved world hunger, provided peace and eternal salvation to InfoPath users everywhere. Fair enough? :)