One of the problems with Lightroom and other Adobe products is that you can't buy modern versions outright these days - only on a monthly rental basis. However, I managed to get a copy of Lightroom 4 outright on a CD from eBay. (Mac OS 10.6.8).

I also managed to download an old version of Adobe Photoshop CS2, which is an old, but still viable product. I think that Adobe have started to pension off old versions of their software and sell them outright.

There's also a free, open-source package called Gimp that does much of what Lightroom does, but I've not used it much after getting Lightroom.