Is buying a refurbished computer a no go in terms of security and privacy?

I've found a reseller specialising in thinkpads, most in A+/ As new condition, and I'm very tempted. However, I need my computer to be secure for documents and I was wondering what the general impression is on refurbished computers, or what I can do to check/ resecure it if I go ahead and buy it.

computer go privacy security terms