Greetings,
I had a similar site to this...I have a client that rents properties and so I had to create something very similar for him.
I use PHP Thumb to resize the images (
http://phpthumb.sourceforge.net/). It’s super easy to use. Just download it to your computer, unzip it, ftp it to your server and when you call the TV for that image, just use PHP Thumb to resize it on the server.
Here’s an example of a site I just recently built using PHP Thumb to both create a thumbnail of a property and to resize the image when it is enlarged with lightbox:
http://rent2ownhomesonline.com/Available-Properties.html
The client I gave Manager privileges to uploads the images in the Template Variable section (there are 7 different TV’s...one for each image), and PHP Thumb handles resizing it according to the parameters you set.
Then if you notice on other pages throughout the site, the different properties can be featured using Ditto. Those individual property images on the featured properties are then resized using PHP Thumb.