Yeah i agree with Xoax, pretty much impossible to find a free game engine.
I think you should work on something else , you don't seem to be a coder or
graphics designer(it will take many months to master coding and modeling).
Also there will be other cost for *Master server hosting(I think you have to pay for server hosting) and modeling program.
So um good luck i guess..
It isn't impossible at all considering that there are dozens.
Also, you don't really know me, so you couldn't really say that "I don't seem to be a coder or graphics designer."
I realize it could take months or years to learn a language which is why it is a summer project. I also own MS3D which is a reasonable modeling program with many exporting options. Master server hosting on a free engine I doubt costs money, especially if you look at games like AssaultCube (Free game) and BLv0002. (The engine wasn't free, but I think using its server was.)
I am also working with a friend, which is a thing that some of you seemed to miss.
This is mostly a learning experience, I am not expecting to create a successful free game that has very little bugs in it.