If you can afford it, I'd highly suggest subscribing to the CF Journal (http://journal.crossfit.com
w/f/s) - there is a recent article on there about what equipment is most useful as well as the average cost of the equipment. The article suggests that you can get a good variety of equipment that will enable you to do 80% of the WOD's on the main site for about $1500.
Here's the link to the article (I think you have to have a subscription to actually download it - some of the articles are free though).
The yearly subscription is $25 and I've gotten my money's worth out of the articles and videos and I just joined about a month ago. The articles and videos are not just on the movements and how to do the, but also include info on nutrition, motivation and other CrossFit related stuff. I've found the information provided there invaluable in getting me started on a CrossFit lifestyle.
Also, there's always an option of renting a storage unit and working out of that - here's a guy in Baton Rouge, LA doing that very thing (see link below)
He's got a rack and bumper plates and he works out of his 10x10 storage space. Interesting plan, but it's working for him.
Good luck with the program and let us know if you have additional questions.