Re-painting ruins the value -- or at the very least seriously compromises the value of most vintage bikes

On the higher end, you wont be able to tell what it is anymore unless it is a bike with distinctive lug cutouts or features,

On the lower end, you will never realize your time and effort back out of it

---- but in both cases, - if its a labor of love and you just want to paint it (there is a guy on the boards who did a striking polka dot paintjob on a bike for his wife/daughter/girlfriend (i forget) )-- and it looked fantastic!
I had one of my old racing frames re-painted as well after it needed some frame repair, but i documented it with plenty of before and after pictures , even though i will never sell it -- this basic single color paint job with decals was over $500

And then sometimes a bike is so thrashed that you dont even want to look at it, much less ride it -- here is where a powder coat job makes a bit of sense for a rough use beater or grocery getter