That depends on the type of guitar you have. Steel strings aren't going to be that rough on his fingers. Anything he plays will come with some amount of pain, but it really isn't much at all. And it certainly won't HURT your fingers. If you have a classical guitar, stick to nylon strings. If you have a steel string acoustic, stick to steel strings. Otherwise, you can actually do some damage to the guitar by stringing it different materials.
The difference in materials results in a vast difference in tension of the strings. This difference can often result in a neck becoming bowed, or, in extreme cases, cracking in the guitar, especially on the top above the soundhole. Whatever the guitar came with, stick to that. He'll be just fine. =)
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I love science, and it pains me to think that so many are terrified of the subject or feel that choosing it means you cannot also choose compassion, or the arts, or be awed by nature. Science is not meant to cure us of mystery, but to reinvent and reinvigorate it. -R. Sapolsky
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