If you wait until you retire (unless retiring happens in 5-10 years maybe), you might not be able to afford the gear.
Stuff is pretty expensive even now, depending on what you want, what you can get, and such. Or, maybe you'll get lucky - several years ago I scored an Altair for $200 from a local electronics junkyard; later I went back and scoured it for a bunch of S-100 cards (as is, it came with a full complement).
Later I got some things off ebay, and even some free items from some other collectors - all I had to pay for was shipping. One strange beast was a 6502 cpu PCB (unpopulated) - I am not sure if it is compatible with the Altair's S-100 bus layout, or if it is meant for some other machine (the bus wasn't as standard as one would like, unfortunately).
Anyhow, good luck with your dream - just collecting the stuff can be fun enough!
When I retire and I have more time, I'm going to fill my house with Cromemco-era gear and do all the things I always wanted to do back then.
But first, I have to convince my wife that S-100 bus machines are mid-century modern, so she'll allow them in the door.