My understanding is that TZ was a dog when it was released, not sure if that would ring true in today's market, but food for thought.

TAF & ACDC are proven money-makers on location from what I've been told.

Try and pick machines that have good reliability history. Toys are nice, but the more toys a machine has the more there is that could potentially go wrong.

Whatever machines you go with though try and take the time to service and clean them properly and regularly. Don't become the focus of a "OMG, you should see the torrid shape of this LOTR I just saw out in the wild at RadiatorLady's Big Ball Emporium..." thread.

Fish Tales would be another good choice if you can find one in good shape. Really fast ball times if dialed in well.

$5 per 60 minutes of play time, for example. All machines set to freeplay. Not sure how one would enforce that though.