The first computer I owned, purchased with my cash - was an Ohio Scientific C4P.
6502, 16K RAM ( it had the upgrade ), one channel D/A converter (never used that), and eventually I installed the color board.
What surprises me now, but I didn't understand at the time: I bought that computer on credit at age 16! The physics teacher at the high school had a small computer shop. He let me take the machine home for $20, and a deal to pay on it every week.
I paid it off in 4 weeks (I had a fairly good job for the era), but he was prepared to let that take a year.
Imagine doing THAT today!
It was also the machine that first turned me into a "programmer" - I claim that because I actually sold a game I made for that machine for $5, to the store that sold the computer to me - loosely based on the first Star Wars film - the Death Star run. 3D wasn't really possible (it didn't have individually addressable pixels) - but I managed to create a reasonable illusion (compared to PONG).
Ohio Scientific never "made it" to the big leagues. It wasn't an Apple II - it wasn't even a TRS-80 level of success. They made, perhaps, 8 models - one of which had a 74 Mbyte drive before 1980 (it also had 3 processors, a 6502, a Z80 and one other I don't recall).
The first computer I used regularly, but was actually my father's, was the TRS-80 Model 1. At first it had 16K, but was upgraded to 48K. It was a touchy thing - reboots just because the phone rang. They keyboard had a notorious bounce (you'd hit 1 a, you'd get 20).
The first computer I owned and used in my career (I'm a software engineer / developer ) was a Sanyo MBC-550 - an IBM clone of sorts. I was 21. It served me well, but it was a bit of an oddball. Slightly slower than the PC, physically small - it looked more like a piece of stereo equipment than a computer of the era. The keyboard felt nice, though, and it worked flawlessly for 8 years.