When buying used, especially vintage, the priorities are:
Does it fit?
Has it been damaged/abused/overused?
Components scratched or any rust?
Is it rideable today? Every gear combo function?
What level of components? takes some learning
Will it need upgrades to serve your purpose?
Does it make you smile?
Fair price?
The end.
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Vintage, modern, e-road. It is a big cycling universe.