As above, I can't see paying more than $200 for an 80s or 90s steel frame bike on the local used market (depends on where you live, probably), then another $200 max to repair and upgrade it to my tastes and needs, including excellent new tires for a tour. Can't help with the trailer, but best of luck touring with your dog--some friends do that on their tandem and they all love it, including the dog.