It's a downright beautiful song.

Anyone know who the inspiration was for the song?

Here's what the vault says. Maybe it was simply written about Ingrid - but it might not have been.

Once Upon A Time (formerly known as Bobbi Jo and later 26) is the eleventh and final track on Eric Leeds' first album Times Squared.
A solo piano version of the track (as Bobbi Jo) was recorded by Prince in December 1987 (most likely at Paisley Park Studios, Chanhassen, MN, USA) as a gift for Ingrid Chavez, with whom he was working at the time (the inspiration for the name is unknown). He re-recorded the track on 4 January 1988 at Paisley Park Studios (during sessions for the Lovesexy album).
[Edited 8/28/16 18:35pm]