Five years ago or more, owning a full-frame DSLR was a privilege only for the very wealthy, with prices being in the region of £2500 plus, just for the camera body. Most of us, myself included, started with a crop-sensor DSLR, but possibly had a secret desire to use full-frame but knew it was out of reach financially,
Older full-frame DSLRs have now trickled down into the second-hand market, and it is possible to buy a used full-frame camera such as the Canon 5D (Mark I) in good condition for under £400. Admittedly the older models of the 5D do not have Live View or Movie capability, but the ability to get truly wide-angle shots, the luxury of a huge bright viewfinder, and the low-noise qualities of the big sensor make these cameras very attractive.
The downside is that the lenses designed specifically for crop sensor cameras are not suitable for full-frame use. However, in the case of Canon, the older EF lenses from the film era will work fine on full-frame digital. The secondhand prices of these old lenses are often quite low, in part because the range of focal lengths for full-frame is not very useful for a crop-sensor. For example, a 28 to 135 mm zoom is ideal for full-frame but is of limited use on a crop sensor camera.
I am now a full-trame convert, and hope at some stage in the future to be able to buy a more modern full-frame camera (the Boss says only when she has had that new Kitchen). But for people such as myself on a limited budget, the second-hand route to full-frame is now a realistic option.