What is considered a good candidate for a crescent lift without implants?

Not sure why you would want a lift if "the nipples do not point down, no sagging or stretch marks". A cresent lift will not help all that much.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS) and the American Society of Aesthetic Plastic Surgery (ASAPS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach Trained, Double-Board Certified Plastic Surgeon

Dear cosmo17,
it is really hard to tell without photo or in-person examination. You mentioned that you are satisfied with your breast size and that the nipples aren't pointing down, so you might be a candidate for a doughnut mastopexy. It can be done under local anesthesia.
 I would recommend you to visit a board-certified plastic surgeon for an in-person consultation. 
Daniel Barrett, MD, MHA, MS 

Certified, American Board of Plastic Surgery 

Member, Am. Society of Plastic Surgery