How do you know you’re not buying a used bike lemon?

Former MTB pro Nick Martin started The Pro’s Closet out of the back of his old VW van 16 years ago, and now it’s a multi-million dollar operation with nearly 200 employees, a monstrous warehouse, and roughly 2000 used bikes for sale on any given day.
TPC’s ace-in-the-hole is its Certified Pro-Owned program, which promises you’re getting a used bike that’s been fully inspected, serviced, safe, and ready to go — and it even comes with a 30-day return policy.
The CPO thing has worked wonders for the used car industry, but does this it sense for used bikes? In this uncertain world we’re living in these days, maybe a little certainty is what we need.