I've lost been in and out of the retro console scene a few times, but when ever I sell stuff it seems to be the time when it's all cheap, and whenever I buy stuff it always seems to be when stuff has shot up.
I've pretty much settled on having an N64 because MarioKart 64 cannot be enjoyed any other way
and then a Pi in a SNES mini case with a megadrive, snes and NES controller (all 8bitdo) and a pi in a gameboy case for the handheld games.
N64 consoles are around £40-£80 depending on what comes with them - controllers, power back, memory jumper and what kind of nick they're in
(I bought a clean base, but with none of the bits for about £35 a year or so ago)
There is a guy who does a decent upscaler/hdmi converter for them that actually works, and the S-Video cable that works with the PAL models
Worth a look for anyone that fancies some N64 action via an AVR/HDMI TV