The roar from the back wheel is likely a bad wheel bearing, which costs in the ballpark of $350 to replace. The shimmy could be caused by a number of things, from something as minor as a wheel being out of balance, to worn suspension components. I'd shell out a few hundred for a pre-purchase inspection and have the car gone over with a fine-tooth comb.
1998 BMW 328is
1966 Pontiac GTO
2007 Subaru Impreza 2.5i 5-door
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