I think I found my next beater!

If it's anything like my 1999 Alero, and it is, if the A/C compressor is still the original (unlikely, but in MN who knows) it leaks and needs to be replaced.
That is the same model as the 5th Generation Chevy Malibu Classic. Pretty solid IMHO. I would recommend changing the fuel filter though if it hasnt been changed recently. It is in front of the fuel tank on a suspended bracket. You will need quick connect / disconnect tool to do the job. Should be lots of spare parts for these in most yards, and most anything from the Chevy badged version should fit.

No idea on any of the maintenance history, I'll know more tomorrow when I go take a look. I know these cars like the back of my hand, I plan on bringing my scanner and checking for codes. I'd be willing to bet it's got a security system issue causing an intermittent no start.

3100 intake gaskets are simple. 3ish hours give or take. The full set with metal lowers and valve cover gaskets is $39.99 on RA, If it needs to be done it's no big deal.

As far as these cars being used mainly by people that tend to slack on upkeep, the Oldsmobile's tended to be owned by the older crowd while the Malibu's were beat to snot. Given the apparent cleanliness of the interior, the 129k miles, and the general demeanor of the seller lead me to believe that this was more a backup car than a beater for most of its life.
I think I found my next beater . 🤣
Yeah the passlock issues were VERY common on these, and the fix is to cut two little yellow wires that lead to the ignition switch while it's running. (Don't follow me verbatim but it's something like that.)

The symptom is it sounds like it wants to start, almost starts, or starts and runs for half a second before stalling. Meant to aggravate the thief. An override is to leave the key on for ten plus minutes.
Pretty sure this 3100 predates the HG issues. Did you really get this for $500??? Here, cleaned up, that vehicle would easily pull in $4000, especially if someone was trying to put their kid in one for high school and college. I’ve seen that engine and trans take a ton of abuse with little to no maintenance. IMO, stiffer engine mounts and suspension bushings with a mild shift kit would make a very acceptable and fun DD. I dig the color too. clean it up, flush all the fluids, shocks all around, it should be GTG!