I wouldn’t trust the air pumps that have a pressure setting on them (ie you dial it to 36 psi, stops when that is reached), they are notoriously unreliable and can overfill tires (here in NJ, most places with air pumps are no longer free, as they once were, they charge between 50c and a buck, and they don’t have pressure settings). Your best bet is to get a good quality air tire gauge, the old pen ones if made right are great, the gauge ones work okay, but don’t buy the buck store ones, a good quality one at an auto parts store is around 5, 6 bucks. In terms of filling tires, I recommend, not the old fashioned one where you use your arms, but the one that you use your feet (usually lies on the floor and has a lever kind of thing you step on to pump it up that returns up automatically when you let it go), they are compact and a lot easier to use (or you could get a small battery powered one that uses the 12v in the car to power them).
As far as cars go, both Kia and Hyundai if you buy one that is relatively late model are good cars (I believe Kia is made by Hyundai, it is a sub brand kind), they used to be crap, but Hyundai spent a lot of time and money on improving their quality, when they realized that having cheap prices, as they once did, with bad quality wouldn’t work, plus Hyundai has moved into the more expensive markets. Word I get from my network is they are pretty reliable and a solid car.
Some of the best deals may be a late model lease when they are returned, when you buy off a lease the depreciation is out of it, so you can get some good cars plus people tend to take care of leased cars more than the ones they buy, because they get hit hard when they are returned for wear and tear. A lot of leases limit mileage to 10k per year, so you can get a car with 30k for pretty cheap, and 30k is practically new these days.
With rental cars, the conventional wisdom was you don’t want to buy them, that they were abused by people renting them and so forth. If this was 10 years ago or before, I would have told you to run the other way, because cars back then weren’t quite as reliable as today, and a lot of the late model cars coming off rental car lots were not great IME, these days as long as they were routinely maintained, it is a good option. Put it this way, back in the “old days” friends of mine who are mechanics would see the rental cars after someone bought them, and they would see things like transmissions with burned disk plates in them, driveline problems with CV joints on front wheel drive cars, leaking engine seals, you name it, they don’t see that now, in part because the cars don’t require all that much maintenance. Most rental car companies ditch their cars to upgrade to the current model year, so it is not a bad deal at all. The cars may not have the options you want, most rental cars for example don’t come with built in nav computers (so they can charge you extra to rent a garmin or whatever), and if you are looking for a zippy car you won’t find in general the more powerful engines, but if you are looking for a regular car, not bad at all.