What you want to do man is buy an old school steel bar+steel weights. Avoid these ones that are plastic filled with concrete. You can find those old weight sets at flea markets and thrift stores pretty cheap. Well at least you used to be able to I haven't gone shopping for them in a long time. But I'm sure it's still possible since the weight of shipping them would discourage people trying to scalp them and re-sell on places like ebay. Maybe facebook marketplace fucked up this market to like everything else that has scalpers now who "know what they got".
That said there are tons of people looking to unload stuff like that because it takes up too much room and many people buy it and never use it. Or they have someone that lived with them pass away and since the stuff takes up so much room they're looking to get rid of it cheap. Hit up yard sales I often see old sets at those when I pass by. If you have a truck there is no issue in transporting them. You'll also find a lot of cheap deals on stuff like stationary bikes, speed bags, heavy bags and misc. equipment.
They are much much better than the sliding weight sets and the cheaper (newer) modern dumbbell+bench set-ups with those terrible plastic filled weights.
Now that said here is something else I think you should consider:
You don't need a proper gym or weight set to work out. In fact, I find such things counter productive in a lot of causes for building up real strength. Plus working out inside can be pretty depressing. Instead I suggest trying out things like the following:
Have a mountain close-by? No better cardio than hiking (or running) up a mountain and back down. Stuck with flat land? Then you could run around a local field or track instead. Usually, the public tracks also have bars for pull ups as well and other misc. stuff like that.
Want to lift? Plenty of farmers love guys that want to show up and toss square hay bales four times every growing season. Near a wooden area? Plenty of large fallen branches and sometimes cut up logs out in those places you can lift. It's uneven weight as well which much harder to lift and gives you more of a work out. Lots of old tractor tires (and other large tires) around that you can use for lifting and cardio at the same time. Very easy to make you own "dumb bells" out of fallen trees. All you need is an axe which is a work out in itself. Spend a day using the axe to punch some holes through those logs. Then you can use the logs to lift/carry back and forth across your yard or if you find an old tractor tire you can push it back and forth across your yard by flipping it over and over again like in the strong men contests. Maybe your neighbor needs a tree fell. Offer to do it for him (he might even pay you!) then instead of using a chainsaw do it the old fashion way with an axe.
Even picking up fallen sticks off someone's (or your) property and stacking them in a pile is a good work out (cardio and lifting for free). Then at the end you get a nice bonfire to light and can invite your friends over to enjoy it.
Even if you don't want to go through all of that: push-ups, sit-ups, doing pull-ups on a local tree and all that kind of stuff is a much better workout than you could ever get at a gym (or home gym).
Just some things to consider. A lot of people these days are to focused on lifting in a gym to look good. Fact is, a lot of the gym stuff isn't that great for you and a lot of it doesn't build real strength. Consider a treadmill: awful on your knees. Boring. Running in one spot watching TV or listening to music. Instead, why not walk/jog/run around your neighborhood or a nice field or a nice hiking trail? Get your workout, get some sun and get out in nature where you can listen to the birds and animals instead of whatever songs you grew bored of years ago.
You know what the best work out for me was growing up? Farm work and riding dirt bikes/ATVs. I stayed in amazing shape growing up tossing hail bails up to waiting men standing on the top of trailers (with hay stacked sometimes 10 bails high on top of a trailer that was already 3-4 foot tall) and riding my dirt bike/ATV hard for hours on end. That plus roller skating multiple times a week and playing some sports like roller hockey kept me in amazing shape. I didn't look like I lifted and would have never looked good enough to grace the cover of a magazine. But I was much stronger than everyone I knew that went to the gym every day and I was in better shape than all the guys playing sports for my local school(s). When I tried out for football I had much better cardio than my peers and I could hit much harder than them. Since I'd spent the last several years playing roller hockey and working on the farm. While they were playing middle school football and always in the school's gym.
I remember the first time I hit a guy in football practice. He was supposed to be one of the toughest D-line men they had. I nailed him using what I'd learned from checking people while playing roller hockey over the years and I hit him so hard I nearly made him cut a flip in the air. He didn't want to hit me anymore after that.
