We are a small business and have been working in the CS2 suite forever. We had someone do some work for us in Indesign CS4 and are looking to upgrade to that version so we can work with these files as changes happen. If we upgrade to Indesign CS4 will it still be compatible with the rest of my CS2 programs (Illustrator and Photoshop). Placing files and such. Thanks in advance, I know I am way behind here but it is what is cost effective for now.
You'll have no problem placing your CS2 photoshop or illustrator files, but you will have trouble finding a copy of InDesign CS4.
Adobe only sells InDesign CC (by subscription) or InDesign CS6. You might find boxed legal copies of CS5 or 5.5 from a vendor like Amazon.
You should be very wary of buying older Adobe software on the Internet or eBay. Many copies don't have a legal license and may cause you problems in the future. Caveat emptor.