Tenants interested, smartmove not helpful. What would you do?

[Tom V.]

I have a couple interested in a unit. They did a smartmove credit check, and both came back with "Not enough info".

They make well in excess of the rent, about 5 times. Verified income.

But there's no credit cards, no late bills, no loans, no anything to judge them on. 

On the plus side, no criminal history or eviction history. All a-ok there.

References check, and all else looks good. But smartmove won't give a recommendation.

They seem nice, but we all know how that goes. Googling them shows nothing unusual, no odd FB or G+ accounts.

What would you do?