Use Cornell Library's Services and Expertise
Use the Reference Librarians at Olin:
They can help you locate archival collections elsewhere, but also track down the vast numbers of digitized sources that are already available to you. Don't expect all of your materials to be available online, but if you are dealing with rare books, newspapers, serials, or other sources, you might be able to find digitized versions.
Talk to Inter-library Loan:
Even if archival collections are not digitized, heavily used or very important collections at most institutions are available on microfilm, which can often be lent to Cornell patrons via ILL, or have single reels or some sections of reels sent to you via PDF. Olin has great microfilm scanners that can convert microfilm to PDF as well, so that you can save materials as needed. ILL might also request single items from archival collections. It is always worth a try. The ILL staff will work diligently on your behalf to get the materials you need.
Should I Pay or Should I Go?
Even if ILL can't get everything for you, if you have looked over a finding aid and determined that you really only need a few folders at an institution, or your plan is to photograph from a collection and then run back to Cornell to sort through it, it might not be worth making a trip. Many U.S. institutions have on-site scanning services that will scan a few folders for you at a cost. The cost is usually pretty high: you are paying for staff time to handle materials that are unique and often fragile and can't just be run through a photocopier.
Independent Research Services:
If there is a larger amount, you can also consider hiring an independent researcher to photograph for you. If you contact a repository, they might keep a list of contractors on hand. Graduate students from the local departments are often willing to make a few extra bucks as well. The costs vary from $25-$40 an hour, negotiable based on how much research skill is needed for the job.