It seems you're wanting an on-site solution.
You'll need a piece of OCR software and therefore a license if you're wanting to search within a page for specific text. If you can do with just indexing your full page images and using that as a system for finding a specific body of text then you'll just be looking at shelling out for the capture software license. However, the larger the office, the more complicated indexing and the need for OCR becomes, unless you've got a fantastically simple paper filing index system that can be replicated through the scanning software and storage structure.
Approximately how many images are you looking at that need to be scanned already, and how many per day, ish are you looking at that need to be added into the system?
Would you want them as .pdf, .jpg, .tiff? Full colour, greyscale or mono?
You will never ever create a paperless office, you'd be surprised at just how much paperwork is created in keeping your office 'paperless'.