Nothing at all wrong with used BCs. If they will hold air for an hour or so (fully inflated but not over inflated- be careful using a power inflator), if it inflates and deflates using all of the associated valves and there is no visible signs of damage, fading is ok, it's good to go. Even one that leaks is not an immediate reject, a grain of sand under a deflator or one that is a little loose will leak. Those are common problems and nothing a good cleaning or tightening will not fix. Same goes for the power inflator. Those give problems from time to time but are easily repaired or simply replaced ($35ish ).
As for recommendations, you are going to get a wide range of opinions, some are better than others. I would suggest you decide what your major diving is going to be and buy with that in mind. Travel to warm spots is best done with a lightweight BC, cold water diving with large tanks is a different animal are really requires a different BC. One BC will not do it all well, regardless of what some would have you believe.