This is a difficult one. I met my husband and it did go very fast, he was wonderful, etc. A job came up seven months into our relationship, where he lived, which I applied for. Fortunately, I did not get it, because it would have been madness; it took a couple of years to see the real him.
On the other hand, I know two happily married couples who knew each other at uni, and got together some years later, who are very happy.
I think the risks lie in the fact that you are doing all the giving. What protection do you have if you pay half his mortgage for seven years, and it goes tits up? I would at the very least get legal advice on this.
Secondly, you say you are happy to wait seven years for dc. What happens if your biological clock starts ticking loudly in a couple of years? Also, if you start your family at 34 or 35, and want more than one dc, you are risking fertility issues. So, is there a way of financing having dc before seven years are up?
Thirdly, what is your support network where he lives, and how would you meet people?
And lastly, as you knew him at uni, I am assuming this 7 year thing is a second degree? What on earth is it? I can only assume medicine? Or is it a Masters plus PhD which should not take seven years.
My advice would be, if you go for it, get your own place first, see how it goes, then if all is well, buy a house together, which is both of yours and get a solicitor to draw up a document of who paid what into the new property. I would not move into his house and start paying off his mortgage after a few months, on a wish and a promise, having given up your support network and everything. You need to establish your own life there, if you go.