Let's face it, mortgaging the house to purchase commercial software is not an option. In lot's of instances, there are high quality open-source software alternatives that are every way as good if not better than its' commercial counterpart.
Finding the alternative is sometimes a challenge.
Over at http://www.osalt.com, they maintain a list of open source software and looks like a good starting place in your search. For instance, if you’re looking for an alternative to Photoshop, you can see a list of open source alternatives that are available that may fit what you’re looking for