Bike fitting and buying a used bike

I'm looking to get a bike for around $1000, and I'm thinking I'll get the most bang for my buck buying a used bike. I want to get a professional fitting to make sure everything is just right before I start IM training, so I recently wrote to a fitter that came recommended on this forum and asked whether to get fit first and then buy a bike, or to self fit for buying a bike and then bring it in to get it fine tuned. He said to get fit first, as long as the info that comes from the fit can and will be used to inform the purchase. I asked him to clarify why I might not be able to apply the fit info to the purchase, and he responded:

"The results of the bike fit are recorded using XY standards. That is how high the bars are and how far forward they are relative the BB. XY is used by fit technicians because it makes communicating the bike fit more simplistic. Bike manufactures do not yet list a range of XY coordinates that are appropriate for a given bike. Extrapolating fit based on the TT, Stem, and Headtube sometimes gets a tad tricky but is possible."

Has anyone bought a used bike based on a professional fitting? How did it turn out?