I work at an office.   My office with a couple employees.

I started making websites while working at a full time job.  Eventually I had to quit something and quit the job.

You sound like a dedicated person.  I respect the posts that you make here.  You are obviously good at your work.

So, think about building a couple websites of your own.  You might need to work for someone else while you do this but eventually you might be able to work entirely for yourself.

is there a standard practise/best practise for SEO to do this and ensure Google doesn't think i am plagerizing content etc

The best practice is to contact the author of the content and obtain permission.  That is the legal way to do it.  Otherwise you are committing copyright infringement which can land you in court.   If the owner files a DMCA with google (millions of pages get a DMCA each month) your page will be removed from the SERPs.  If you get a few DMCAs filed against you, it is possible that your whole site will be removed from the SERPs.

If you start republishing a lot of articles, even with permission, without setting them to noindex, then google will see your site as a duplicate content site and will either filter your site from the SERPs or hit you with a Panda problem.

Even better practice is to write unique content for your website.  Then nobody is going to take you to court, nobody will file DMCA, google will not filter you, and google will not Panda you.  If you can do that repeatedly with excellent content that visitors love then you will be in a position to make buckets of money.

Yanking a couple of articles that make up a tiny amount of your traffic should not be a problem unless those articles have a lot of links or other off-site assets or unless those 0.51% of visitors do a lot of buying.

If you are worried about this, have someone write same-topic replacement content and toss it up on the same URL

I bought a domain that had about 25% infringed articles.  I took them down right away and tossed up replacement content and the rankings held.

are there any SEO downsides to not having any substantive content on the home page

These are not thoughts.  They are facts.  If you have a homepage with just a few words you will get a certain level of traffic.  However, for almost every relevant word that you add to the page you will probably get more traffic as those new words combine with existing words to create many more combinations of new queries for which you are relevant.

Here is a short story....

We had a lot of pages that had one sentence descriptions of photos.  They got a little traffic.  When we increased the text content on those pages to a couple hundred words the rankings increased and the traffic went up by 10x.... When we upgraded those pages to 2000 word articles with several photos the rankings went up again and the number of visitors went up significantly - some to thousands of visitors per month.  Now some of these pages get more visitors in ten minutes than the one-sentence pages received in a day.

Our guess is that if the home page doesn't have much copy, that odds are that other specific pages will tend to perform better for non-brand search terms, which seems OK.

I think that your guessing is harmful to your wallet

If people DO find the homepage, it would likely be a brand search or an ad referral, in which case the minimalist, non-copy design would be conversion-friendly. Does that theory hold any water?

Most of the visitors who enter my site by the homepage are coming from queries that have nothing to do with my brand.  My homepage looks closer to the LA Times than to what you are describing.  I want my visitors to say DAMN!  Look at all of this stuff!

The retail sites where I have this convert really well.  I would be very hesitant to use your proposed homepage unless I was selling just one item on that website.

"(which will presumably have more SEO benefit)"

I agree.  I would go with putting the KB in a folder on the clients domain.  That way, links into the KB will be hitting the main site instead of a subdomain.