Through a preference page, or using style sheet switcher, the user can switch the multi-column view to a single-column view with big fonts.
Allow the user to zoom or increase the font size
Allow the user to change colors. Many users want light-on-dark text rather than dark-on-light text
Re-arrange content. Should allow user to use alternate style sheet or user-defined style sheet to change your multi-column layout to single-column layout
Do not do anything special to images. Do not assume that low-vision person won't be interested in your images. Don't try to hide, shrink, or enlarge your images.
Too much navigation on a page is a serious usability problem. If you think you need a drop-down menu, you need to streamline your site.
Do not attempt to create a separate site / version for low-vision users. You may create a separate style sheet for low-vision users to enhance accessibility, but the content should be the same.
As it turns out, what you are doing for low-vision users is similar to what a handheld browser must do when confronted with a wide, multi-column page. It too must selectively reorder and hide components so the page content can be enjoyed in a single column.