One problem if you buy old or new is finding a competent service technician to repair your equipment, which are becoming few and far between is this disposable culture. Younger people prefer to deal with computers than get involved in radio - many of which don't even know that 2-way radio even exists.
Using the CB/freebanding radio world as an example. Most 10/11 metre modern "export" multimode rigs are just junk. Poor quality control, bad alignment, and a lot of frequency instability for modern standards. If someone is a keen on freebanding, it would be better to buy a HF amateur rig that has been widebanded.
A more sensible approach is to buy equipment that does the job, whether old or new. Flexibility in choice rather than going for the latest bells and whistles. Better to buy gear that can be written off in a few years. If it costs an arm and a leg may be you are beyond your budget. Another approach is to use modern up-to-date gear for every day operating and use the old rigs for that occasional blast of nostalgia. A bit like having a modern hatchback to get to work and back, but in the weekend polishing your 1970's classic car, giving it a good rev up and a spin down the motorway.
Good examples for secondhand purchase:
* Big old meaty 20 to 30 amp linear regulated power supplies
* Old 2m/70cm rigs that don't have CTCSS (buy a generic ctcss encoder board to upgrade them)
* Old skool Uniden SSB CB radios (if you have a good "rig doctor" to maintain them)
* Antennas that haven't had much use
One thing that should always be purchased new is coaxial cable. Water slowly enters and corrodes down through the cable.
The following video is a tongue and cheek reflection of the combination of old and new stuff: