It hasn't been mentioned (much, yet) but if the Saudi takeover of Newcastle goes through, it won't (and can't) lead to a massive spending spree. FFP still exists, domestically and in Europe, and it's not going away. A summary:

https://www.mailonsunday.co.uk/sport/football/article-8257335/Premier-League-UEFA-insist-Newcastle-adhere-spending-restrictions.html

Top sports lawyer @FootballLaw also gets into the detail of how FFP will restrict Saudi spending, in a piece here: https://www.mailonsunday.co.uk/sport/sportsnews/article-8257447/Newcastle-adhere-spending-regulations-compete-Europe.html

Here's the crux of it. In Chelsea's first three years under Abramovich, CFC lost £308m. In Man City's first three years under Mansour, MCFC lost £395m. They succeeded in buying success. Under UEFA FFP, Newcastle can lose £26m in three years.

IMO, one of the most thoughtful examinations of the Saudi motivation (and plans) for the Newcastle takeover, both in terms of detail and balance from @DuncanCastles, was in this podcast. The FFP limitations are dealt with here too. https://www.spreaker.com/user/12250300/newcastle-takeover-and-deal-details