Teleprompters a dime a dozen now
Back in time, when puppies were the oldest animal, I had a side business running a teleprompter rental/opertor service. Prompters were expensive and complicated rigs, not quite as exotic as steadicams, but still, not a thing everybody carried as part of their equipment list. So I invested in a modest system and kept it low-budget and affordable, a little less than the cost of a camera rental for the rig, and a day rate for myself if they needed an operator. I was the only guy for a 100-mile radius.
The 386 laptop and DOS software I ran was pretty straightforward, and you could rent just the crate, but adding me to the job was "insurance" that everything would work and be ready if something suddenly changed on-set. The prompter monitor was a converted black and white CRT motel/RV camping TV that had had the coils reversed on the electron gun. The CRT was good and bright. It was also 12-volt capable, which no other prompter in town at that time could claim: I advertised that someone could do a reading from the middle of a cornfield if they needed to. (That's not so far-fetched when you consider how much money gets spent in the midwest advertising ag-related products).
It made back it's investment, and a little more, but never turned into the huge second income I'd hoped for... but it was better for me than the weekend wedding gigs I was doing for extra money, because I could sent out the crate and get a check and still have my weekends to myself and my long family. That business is retired a long time now, but the sled and mirror rig is still in a crate in my basement...
But recently I went window-shopping for prompters on Amazon and man, are there suddenly a lot of cheap little rigs out there - many of them geared around a DSLR, so they're small, and often fed by a smartphone or tablet as the image source. The software is cheap too, even free., which wasn't the case back in the day. At under a hundred, and even in some cases, only around $50 for some more DIY-level stuff, the you-tubers and vloggers can afford to own their own pro-level micro rigs quite easily now.
Those rigs are a little small for pro field shooting, where the talent might have to work from more than six feet away, still, LED flatscreens have made prompters really light and portable now, and even a broadcast-level rig for full-size cameras is affordable enough to buy rather than rent now; around $400-$600 for something we'd have paid $2k for, back in the day.
There are still people out there offering prompter services, I guess. Certainly the cost of the gear is not a barrier to entry. But I don't see it a an economically viable business model myself any more, when it's cheaper to own. You're paying for convenience and the extra warm body on the set now, if you rent it.