Earlier this year I had the chance to purchase an excellent-condition Rolleiflex 3.5 (K4A) with full set of filters (coloured, U/V, etc.), a Rolleinar close-up lens, everready case, leather bag, and original papers for a total of $635 AUD ($445) on eBay. It was a great opportunity and an even better deal.
The image-taking mirrors and light sealing in old Rolleiflex cameras can begin to show degradation, so be aware of that if you purchase second-hand or via the internet. The Rolleiflex is largely user-serviceable if you have a general grasp of mechanical repairs and feel comfortable tinkering with mechanics.
My Rolleiflex features a 75 mm f/3.5 Zeiss Tessar lens, and shutter speeds from 1 to 1/500, bulb, and a working self-timer. The lens shows great colours and contrast, and provides sharp images when shot open at f/3.5. The viewing lens makes it easy to focus and compose images, and I do not find myself focusing back and forth excessively.