It really depends. My father found my old consoles in the loft and I decided to get them working.
- PlayStation 1,2 and Dreamcast are easy to get, easily to repair. Normally the biggest problem will be CD/DVD-ROM drive that is bad. These consoles are extremely reliable other than the DVD/CD drive. Repairing such as this are simple and can be done in literally minutes, with a screw driver.
- Games are relatively inexpensive for PS1, PS2 and Dreamcast. Yes Marvel vs Capcom 2 and Castlevania Symphony of the night will £500 for a copy, but the vast majority of games can be found in Good Condition for £5-20. Absolute mint condition games will be about £30-50. I buy a couple of games a month for each console and have a nice small collection of classic games (not anything too crazy, but decent).
- I was missing cables for the consoles (long since lost). I got official controllers, and cables for reasonable amount of money. Memory cards were cheap. I did have to take apart the old controllers and service them, but again nothing major.
- If you have a slightly older (late-2000s/early-2010s) LCD TV, the upscaler will actually work properly and the games look pretty reasonable. You can get HDMI upscalers for a reasonable price for these consoles. Cheap upscalers can be bought online for PS1/PS2 and Dreamcast and the results are "OK".
Emulation is obviously easier, with a few caveats. You must find a BIOS for the PS1 and PS2. These can be easily found with some googling. Also DuckStation has licensing doesn't allow it to be repackaged for your <linux distro>, so you have to use their app image or download & compile yourself. Which is a bit annoying, as I don't really know what to do with AppImages.