Can someone suggest the cheapest one that isn't junk?
I just want to ride in basement 30 mins. a few times a week.

I have a Blackburn. It's very basic, just a resistance knob. It's many years old and the bearing is getting noisy but I don't use it since I retired.

I friend had one with a fan for resistance and you had to remove the front wheel and mount the fork to it. I borrowed it years ago and it was fine.

Performance has a sale on one for $100 but it says it's back ordered.
Saris Mag Trainer (Magnetic Resistance) - Performance Bicycle (performancebike.com)

I picked up a basic mag trainer off of facebook marketplace for $20. It was like new and came with the front wheel riser block also,

Lots of people have perfectly good dumb trainers sitting unused because they have upgraded to smart trainers. Back in the day, I found my Kurt Kinetic Road Machine trainer to be solid to the point of indestructible. WIth the InRide sensor, it was even pretty accurate and I could use it with apps like Zwift. People sell these used for $25-$50 or so. Look on Craigslist.

As MinnMan said, look for a used Kurt Kinetic or CycleOps on Craigslist or Facebook marketplace. They're top of the line options that you should be able to get for under $50.

If you have a local cycling listserv, you can solicit there - might even get one for free.

I have a basic mag trainer that was purchased from the original performancebike.com. Similar units are available, Travel Trac and others. If it is something to be used occasionally, and the noise is not an issue, it may be fine for you. I have no clue about trainer pricing recently.
I did not like watching video or trying to read while on a stationary, but I did find doing intervals helped to break the monotony, and they are easier to do properly on a trainer.
If I thought I would want to ride indoor more
often/longer-term, I would consider spending more dollars for more options.
Adding in, I have been using my mag trainer more often while recovering from a couple of surgeries. It is very stable, I have one of the front wheel blocks. I found I still do not enjoy it, 10 to 15 minutes at a time usually. I know I still prefer to be outside riding, which I am now doing more of.

Any interest in rollers?

Check your local Craigslist.

They are usually on there for $0-$50

No pref.
Compact preferred

Around here, the good, old-style trainers are long gone from Craigslist, for many years. Probably eBay is a better resource to get something worth bringing in the house, like a CycleOps Fluid2 or Kurt Fluid Road Machine. I wouldn't recommend bothering with a magnetic resistance trainer in most cases; they're noisy and don't ride like a bike does.

agree with used via craigs list. after a season of using it you probably won't after that. too boring.

Like already suggested, go to any local bike swap and/or check out FB Marketplace, Craigslist, etc. You'll find many, many virtually unused indoor trainers of the major brands (therefore good quality) for $50. Did I mention virtually unused? There's always at least a half dozen at our local clubs annual swap. And at least 4 unsold.

I have a set of Kreiler rollers. It's an acquired taste.

But having a smart trainer is, to use a cliche, a game changer. Boot up Zwift or the platform of your choice and join a group ride. Or a race, or a hill climb. But be prepared to be humbled. IRL I am a middle of the pack rider. On Zwift, way off the back.

I have a CycleOps fluid 2 sitting in my basement now for 6 years untouched. My guess is the fluid has leaked out again but I wouldn't know because I can't even reach it anymore. I used it for a few years but as everyone else here keeps saying switched to a smart trainer and never looked back. The last year and a half I used it with Sufferfest and that made it interesting for that time, but when I tried Sufferfest again I found that boring too as it got very repetitive, and going back to those same videos in ERG mode on my current trainer seemed like a big step back. Zwift is the way to go with a smart trainer, and Rouvy if you like scenery changes. And as stated above, these people using it are serious.

amen