I would take job A. If you hold them off for a week while waiting to hear about job B, they might hire someone else. Then if job B doesn't come through, you'll be without either one. If you get job B, call A and tell them you took another job. People do it all the time. Employeers know they are not the only place you applied at. Every place I've worked at have always hired more people then they actually needed because they know not all of them will last. Same with a big company DH works for, they had twice as many people go to orientation then they had slots open. When they took a break towards the end of orientation about half the people didn't come back.