I learned to program on a TRS-80 Model I. And for almost any normal need, you could get by just fine on it. You could program in BASIC, Pascal, or Z80 assembly, do word-processing, play amazing videogames and text adventures, or write your own.
There's still people using their TRS-80 as a hobby, TRS-80 Trash Talk podcast, TRS8BIT newsletter, making hardware like the MISE Model I System Expander. With the latter, it's possible to use it for some modern computing problems. I listen to the podcast out of nostalgia, but every time the urge to buy a Model I and MISE comes over me, I play with a TRS-80 emulator and remember why I shouldn't be doing that.
If that's too retro, you can get a complete Raspberry Pi setup for $100 or so, perfectly fine for some light coding (hope you like Vim, or maybe Emacs, because you're not going to run Atom on it), and most end-user tasks like word processing and email are fine. Web browsing is going to be a little challenging, you can't keep dozens or hundreds of tabs open (as I insanely do), and sites with creative modern JavaScript are going to eat it alive. It can play Minecraft, sorta; it's the crippled Pocket Edition with some Python APIs, but it's something.
I'm planning to pick one up, case-mod it inside a keyboard, and make myself a retro '80s cyberdeck, more as an art project than a practical system, but I'll make things work on it, and I want to ship something on Raspbian.
"It was hot, the night we burned Chrome. Out in the malls and plazas, moths were batting themselves to death against the neon, but in Bobby's loft the only light came from a monitor screen and the green and red LEDs on the face of the matrix simulator. I knew every chip in Bobby's simulator by heart; it looked like your workaday Ono-Sendai VII, the "Cyberspace Seven", but I'd rebuilt it so many times that you'd have had a hard time finding a square millimeter of factory circuitry in all that silicon."
—William Gibson, "Burning Chrome" (1985)
Back in the day, I would work on Pascal, C, or Scheme code in a plain text editor (ed, vi (Bill Joy's version), or steVIe) all morning, start a compile, go to lunch, come back and read the error log, go through and fix everything, recompile and go do something else, repeat until I got a good build for the day. Certainly this encouraged better code hygiene and thinking through problems instead of just hitting build, but it wasn't fun or rapid development. So that's a problem with these retro systems; the tools I use take all RAM and CPU and want more.
These days, I mostly code in Atom, which is the most wasteful editor ever made but great when it's working. I expect my compiles to take seconds or less (and I don't even use the ironically-named Swift). When I do any audio editing (in theory, I might do some 3D in Unity, or video editing, but in practice I barely touch those), I can't sit there trying an effect and waiting minutes for it to burn the CPU. And I'm still and forever hooked on Elder Scrolls Online, which runs OK but not highest-FPS on my now-3-year-old iMac 5k.
For mobile text editing and a little browsing or video watching, I can use a cheap iPad, which happily gets me out of burning a pile of money on laptops. But I'm still stuck on the desktop work machine, I budget $2000 or more every 4 years for a dev and gaming Mac. Given the baseline of $8000 for an iMac Pro I'd consider useful, and whatever more the Mac Pro is going to cost, I'd better get some money put together for that.
I can already hear the cheapest-possible-computer whine of "PC Master Race" whom I consider to be literal trailer trash Nazis in need of a beating, and I'd sooner gnaw off a leg than run Windows; and Lindorks with dumpster-dived garbage computers may be fine for a little hobby coding, but useless for games, the productivity software's terrible (Gimp and OpenOffice, ugh), and the audio and graphics support are shit. The RasPi is no worse than any "real" computer running Linux.
'80s low-end computers barely more than game consoles were $200, and "high-end" with almost the same specs other than floppy disks and maybe an 80-column display were $2500 ($7921 in 2017 money!!!), but you simply couldn't do professional work on the low-end machines. Now there's a vast gulf of capability between the low-end and high-end, the price difference is the same, and I still need an expensive machine for professional work. Is that progress?