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Here are cheapie starter tunnels/chutes. The only word of caution I'd give you about them is not to leave them outside. When you'r done, just squish them down, and bring them in. That way, they hold up longer.
None of these tunnels, including all others posted, are going to hold up to rough treatment. They're pretty much fabric tunnels. They'd be fine for starting out, and so long as you're careful, they should do just fine for what you'll be using them for.
I really do think you and your dogs will enjoy getting out there and trying agility. It really is a lot of fun, and it's great for building a wonderful relationship with your dogs.
As mentioned, that is the one problem with teaching 'formal' obedience... the dogs wanting to work only on one side. So, if you get into teaching actual heeling in your obedience class, the solution to that is teaching the dog to heel happily on both the left, and the right side, so the dog doesn't feel it has to be only on the left side to work with you
The flatwork books we posted will also help with the problem of a dog only wanting to work right at your side, as it is the foundation for sending ahead, and lateral distance in the agility ring, as well as other things.