Folks, I and the rest of the Sentry Studios Team members do have real life jobs. So our spare time is limited obviously.
Now take the development of a 'standard' game engine... if you do it from scratch, then you 'normally' need 1-2 years to get something together that is 'ok'. If you want the newest stuff to be included as well, then you can add at least another year. Normally game engines develop thru years, get updated continously to match the new criterias and hardware surroundings that do continously develop too of course. And... you need at least this amount of time if you do it
full time.
If you now take an engine with all the sources available but several years old and out of further development in terms of regular updates, then you will have a nice base to start with, but you still need to get it on todays standards. And this means some additional years of development, full time.
If you buy a licensed game engine, then you normally buy further developments and improvements too. Means, if you license the current Unreal engine, then you can either buy it as is, or you can license it in a way that lets you get regular updates.
This means that you and your company/team can concentrate on developing game content plus some engine internal changes, but the engine itself is developed and improved by another company/team. And then you still need years for developing a game... and this means that you have two full-time companys/teams working on this game actually, cause you get regular engine updates and stuff alike.
And as yurch already said, you would need folks that have the knowledge about programming graphics, physics and stuff alike.
Now look at a mod team. What a mod team does is using a fully working engine or better a fully working game as a platform to develop their own content
on top of the original. This means that you
only need to develop new content, in terms of codes, 3D stuff, sounds, textures, maps and stuff alike. And this is only the tip of the iceberg of the whole product that then shows up as a mod/TC. This stuff alone consumes a lot of time. Time that many of you will never invest in some sort of hobby such as modding is. Many of you have decent hobbies and invest almost if not all of their spare time for them, now think about this a bit more and I guess you will finally find out how much time mod development really needs. I'm not talking about small mods that add this or that little feature. I'm talking about full TCs like Infiltration. These need a lot of time to develop.... and this is all done within our spare time.
Now if you want to start talking about such things seriously, then please consider all this.... or ... get out the
masta plan from Nukeproof