My goodness, why all the discouragement. If the OP wants to embark on a project, he should be encouraged and helped. If it turns out to be onerous or tedious, he will find out soon enough. I am sure he has the common sense to cull or just do minimal work on someone and go all out on the most important.

People want old photographs copied and restored for many reasons, family history, sentimental value, memorializing loved ones ther they have lost, and/or having copies made to share with other relatives. Ofttimes there are no high-quality images and we have created displayable portraits for passport pictures, poorly crafted snapshots, photographs that were water or fire damaged, and significantly damage on critical details of the face, etc. Trying to preserve the likeness can be challanging.

In our own home, obviously, we have many family portraits on display. We also have a little corner with an antique desk and a few family artifacts where we have many restored photographs of folks we knew and some ancestors that we never met. Whenever we or a family member finds an old photograph of lost relatives and ancestors, I copy, restore if required and add it to the collection. There are more current images too and someof the family resemblances are amazing.

My favourite is a great-great-aunt at her piano. It was a badly faded tintype that required hours of work- we even restored the frame.

Good luck to the OP and perhaps he will post a few examples.

It really depends on what you are gonna do with it as to the frequency of use, how you are going to use it, your expectations and your budget.

In my own case, my studio business does quite a bit of photo-restoration. Before digital, we used a lot of airbrush, hand colouring among other manual techniques. Nowadays, we do most of it digitally. I try to recreate damaged, faded or as-is copied images as authentically as possible in a style or look that would have been done in the era of the original image. The "My Heritage" look is reminiscent of the hand-tinting and transparent oil colouring that was popular from 1930 through the early 1960 and in a few cases, I have seen applied prints made much earlier than those dates. The manual method I am referring to involved making a sepia time monochromatic print and then applying transparent oil paints- like the ones popularized by Marshalls. In the 1940s and 1950, studios employed retouched and colorists that specialized in these treatments. Some almost rivalled nature colour photography of the era and some -well- kinda look like colour pints and that's the look of the Heritage versions. Back in those days, many portrait studios were reluctant to sell colour prints, especially in larger display sizes because of their more readily and frequent possibility of fading. Well-processed sepia-toned prints with oil colouring are very long-lasting. The ones we get to restore are usually physically damaged due to careless storage or water or fire/smoke damage but not faded. So...in my case, 12 bucks per month is a small fee to pay for the amount of time saved in colouring these kinds of prints. It can be used as a stand-alone process or just be used as an intermediate step in a more detailed technique.

Other than business, I love to discover, restore, and display old family portraits for our home. We have a family wall with both current and old images. Every now and again a distant relative or 3rd cousin comes up with a priceless image that I can fix-up, colourize and display.

Adobe introduced colorization as a guided edit in Photoshop Elements 2020. It did not get a lot of fanfare, however since I need to occasionally colorize an image, I bought PSE 2020 despite being a Creative Cloud subscriber. I have worked with the AI based engine in PSE and the new beta engine in PS 2021, as well as trying some of the online options. Some thoughts:
1. While AI does a good job at finding and colorizing faces, it frequently misses areas of an image, or colorizes them radically incorrectly.
2. Both PSE and PS allow masking and spot color picking to allow a human to identify and colorize areas of an image that AI misses or gets wrong.
3. At this time PSE is a little better than PS at finding and picking colors.
4. The select and mask tools in PS are much better than the same tools in PSE
5. PS outputs to multiple layers, where as PSE places the results on a single layer. Having the colorization on more than one layer simplifies the future workflow refining the image and making the results look more realistic.

Just my thoughts

In testing Photoshop's colorizing option, I find that it is easily confused. I will post a B&W image that I took in which I emphasized backlighting. And then I will show two examples. First is the one colorized by Photoshop. The second is colorized by the genealogy software MyHeritage which embeds the ability to colorize images.

MyHeritage photo colorization technology that powers this feature was licensed from DeOldify, created by software engineers Jason Antic and Dana Kelley. See: https://deoldify.ai/

On less demanding images, it seems that MyHeritage still does better than Photoshop on other images I have tried.

The camera I used was a modified Sony A6300 in which the color filter array had been scraped off turning it into a mono sensor. A 630nm red filter was used for the original image.