Always wondered, how do you prove you are capable if you can't own one until you proven you can be safe with one?

Seems a bit chicken and egg to me, unless you have a place large enough to fly that isn't AMA affiliated.

Fly with a buddy cord from one transmitter to the person with the waiver. They can select who is in control with the slip of a switch on the transmitter. Just like training with any other RC plane or helicopter. Used to be you had to fly with someone with a waiver and keep a log of how many flights and time and they would sign off on your waiver. Used to be the issue wasn't concerned about controlling and flying a turbine but the procedure to start (it's not just push a button) without starting a fire, how to handle what ifs, and rules.

Pretty sure you can own one before a waiver. You just can't fly it at an AMA field (at least that's the way it used to work). You can order a plane and turbine right now from chief aircraft without an AMA license or waiver. A large reason fields require an AMA membership is for the insurance it provides. Been a while since I looked but used to be the biggest threat/problem with turbines was fire and to fly at an AMA field they require a suitable number and type of extinguishers on hand at all times. Never got into turbines. Flew giant scale gas up to 42% scale and the only waiver was if you went above 55 pounds, of course that's all probably changed a lot now with the drone regs and such.

Guy at our club just got his.  He went to Kentucky jets and some guy out of the blue worked with him all week and got him his.  He paid the guy for his time but he didn't ask for it.

Bit late to the party. Turbine waiver holder here.

You can own, and even fly turbines without an AMA waiver. The issue comes in two places - Most clubs are AMA clubs, and you have to be an AMA member to fly there (thus, you can't fly it there), and (2) you would not be covered under AMA's insurance if you were to have an accident of some kind. AMA's insurance coverage is secondary to any homeowner's or other policy you have, but can still be helpful in the event you burn someone's house down.

Typically, you can own/build/prepare the model for flight, then have a buddy with a turbine waiver fly it. He can buddy box you on it so you can fly it, and you can even takeoff/land in that manner. Then once you get your signoffs and send in the paperwork to the AMA, you're good to go. There is a minimum weight requirement though, so some of the smaller foamy conversions are usually under that minimum weight, so just something to be aware of.