I tried to reply earlier and then my internet service went out.
I'll recap here. I also bought two green horses earlier this summer as an intermediate beginner trail rider and first time owner. I wouldn't say it was the best choice, but in four months I have had good success and don't believe that green/green has to be a recipe for failure.
Here's what helped me: Watching hours of horse training videos online/reading just as many online articles, scouring this forum, and reading and implementing Clinton Anderson's book.
I cannot stress the importance of groundwork just for the relationship building aspect and to reinforce to your horse that you are in charge. Also, as others have said horses can sense an inexperience or timid rider. I am inexperienced, but I have been determined to ACT confident and I believe that has made a world of difference. I'm also very stubborn so when my horses and I have a disagreement I will make sure I get the last word (unless I feel I'm in a dangerous situation, but I try not to let that happen).
My mare started out being very disrespectful to me. She would turn her butt towards me when I approached, attempt to bite, and constantly pinned her ears. Now four months down the road she is almost sweet and has had a huge attitude adjustment. We're still working on a few things like crossing water willingly and letting me handle her rear hooves, but overall she's a very much improved horse.
My gelding figured out that he can intimidate my kids by trying to run them into a fence, so now I ride him. He tried running me into a fence twice and both times he received a nice pop in the belly and he hasn't done it since. He also tried to have a bucking/rearing fit a couple of weeks ago, but we had a nice little discussion as I turned him in circles and he got over it. This weekend we had a super groundwork session and when I took him out the next day he was almost angelic. Again, we have more work to do, but there is improvement and no one has gotten hurt. Nor do I intend to.
All this is to say that I think if a newbie is willing to put in the effort by educating themselves, working with the horse, asking for advice, and has a decent amount of determination and patience it can work.
Good luck and please keep us posted.