We shipped and left it there for three years with people we met along the way. We flew it to Frankfurt and we arrived the same day. We rode the S-bahn to town and got insurance from the ADAC using a friend's German address, went back to the airport and passed customs, then rode off that afternoon. Easy to do.
Two weeks rental rates equalled shipping costs, by air, from the US west coast to Germany. I can't imagine what three years would have cost!!
We didn't explore buying and riding. I imagine it would take a local address and maybe a local driver's license. And bike prices for the same bike as we shipped were double the cost of it in the US. We bought a second, identical, bike to ride while at home between trips.
However you do it, DO IT! The trips we made totaled about 45,000 miles amd covered most all of Europe from Norway to Morocco and Ireland to Greece. It is an experience we'll have forever that cannot be duplicated in the US. And we have toured it form Alaska to Guadalajara, Mexico west of the Great Plains. We hope to do the East Coast someday, but returning to Europe is the priority when we get some more money.