It makes perfectly sense IMO. But be aware that if you make a bit of a business of it, that people also are going to expect guarantee etc. ...
And try to give price estimates upfront, to prevent nasty surprises afterwards.
When repairing 30-40 year old equipment, I can (and do) give a guarantee exactly on the parts exchanged and my workmanship, e.g. quality of de-soldering / soldering - nothing else. I can not guarantee parts that are that old, I can't see inside and can't judge on the old soldering etc...
And that is exactly what I meant, a repair guarantee on the work done, nothing more.
Like with old cars, when you fix the gear box, then people can't blame you for a broken exhaust pipe a week later.
