It all depends on whether they are all selling the same thing to the same persona. If yes, then combine all the campaigns into one adwords account, which feeds into one analytics account. That way they can get feedback on the effectiveness of different keywords, ads, etc. more quickly (because there will be more data, from all the different websites, all in one place, for a particular keyword).

If they are each selling different things, or to different personas, then don't combine their accounts, because it will just make things confusing and not useful from an analysis perspective.

I'd rather look at it from this perspective: create a different AdWords account for a different business.
For the rest, Lee is mentioning great points.

Hey there! Not sure if you're still looking for an answer here, but nevertheless, here's what I would recommend:

In this case, I would probably build out a separate account for each under a master MCC account. You can technically accomplish it in one account, but since you have different websites & are targeting similar keywords, I would split them out separately.

Hope this helps!

I will go with multiple AdWords account option, but Yes, you can use one AdWords account to advertise multiple websites, but I do not recommend doing so. There are many reasons why advertisers might want to send traffic to multiple websites from a single AdWords account. Two prime examples are serial entrepreneurs and organizations with websites targeting separate geographical regions. Google has no policy against using one AdWords account for multiple sites, but in all our conversations with Google about this subject they have discouraged doing so. Here are three reasons why:
1.One website’s policy issue can kill your whole account: You would be surprised how easy it is to get suspended by Google, even if you are trying to do everything above-board. Google may change its policies or crack down on an entire vertical, or you might not realize you are violating policies until it is too late. Suspensions are so common that we specialize in helping advertisers get their AdWords accounts unsuspended.
2. Your quality score may be damaged: Quality Score is a metric between 1-10 that Google assigns to each keyword. Quality Score * Max CPC = Ad Rank, which determines when and where your ad appears. Google says that there is no “Account Quality Score”. Maybe that is true, maybe it is not, but there is no doubt that when you add new keywords, the initial Quality Score assigned to them is affected by the performance of other keywords in your account. You do not want to risk one website’s poor-Quality Score hurting another website.
3. Using multiple domains can make reporting a pain: Importing conversions and Google Analytics data from multiple websites and figuring out what your per-website metrics are can be tough. Use one account per domain to make your life easier.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath