A football field in a tiny space for flying. I could fly an Apprentice inside a football field, but that's after 11 years in the hobby. A beginner will need a lot more space than that.

I'm going to challenge your friend's thinking. He shouldn't be focused on the planes he wants to fly, be it warbird or anything else. Rather, he should be focused on building flying skills. This is fundamentally a hobby, which means it is primarily a skill and a set of knowledge that one pursues for the sheer enjoyment of it. Also, "as cheaply as possible" should never be a factor in making decisions about RC planes. The most expensive things you'll ever buy are cheap things.

As for which trainer to pick, a lot of it has to do with the normal wind conditions where you live and the availability of instructors. The best investment you and your friend can make in this hobby is an instructor to build your skills. Once you know the fundamentals of flying, you will be able to fly any plane you want.