I am not familiar with the term "buy for" either and because no one else has answered this question in 7 days, I suspect that it is a "made up" term.
If you finance the purchase of any real estate, it will continue to show up on your credit report as your debt even if you put the title into your son's name. If he is late making any payment, it will have a negative impact on your credit and will not affect his credit at all. You having a large debt will making it more difficult to obtain additional credit even if payments are made on time.
I answer lots of questions from people that regret co-signing loans for family & friends. IMHO, it is a way to destroy the relationship. When your son qualifies to finance the purchase of a home on his own, he will have earned this right.
Hope this perspective helps!