I second what @Kate Robb said. There is as much a gap between reputable and dishonest operators in the pest control field as there is in real estate. If I remember correctly at some point during this thread you said you paid less than $200 to get the home treated? Many pest control operators will charge considerably more than that per room. If the unit is truly infested it should be possible for a layperson with a little knowledge to detect. here is a video that might help:
https://www.youtube.com/watch?v=ORR7yAT-Vic
With that being said you might spread some diatomacious earth in cracks and crevices after the tenant finally moves even if you don't see any sign of bed bugs. I've seen rooms that at first appeared bed bug free only to find them hiding in the seams of wallpaper, between a window frame and hanging blinds, cracks around crown molding, etc. In addition to doing the REI thing I work in pest control, I don't claim to be an entomologist but if I can help out in any way please let me know.