rframe
pǝʇɹǝʌuı
Smallest impact on my wallet! I'd just like to log some hours.
Depending how cheap you're trying to be and what your threshold for risk is, take a look around for a used Sonerai IIL. They are simple and low maintenance, relatively fast, can do sport aerobatics, almost all are running 4-stroke VW's with low fuel burn and generally more reliable than the big chainsaw engines on some "fat ultralights" and you'll frequently find them around $10,000 or less. The wings come off but they are also small enough to fit beside/under most any other airplane and you can probably rent a hangar "corner" from someone on the cheap.