If I get the 4*40 kit can I finish the build before getting the engine? or do I have to have the engine to comeplete the plane?

You can build the wing, but you need the engine to for drilling the fire wall for the mount to bolt to. You assemble the firewall in the first step of the fuselage build.
I agree with Bruce the OS46 ax is a good engine for ease of use and power.

The O.S. Max .46 AX is a wonderful, powerful engine that is easy to tune. The Thunder Tiger Pro .46 is also a wonderful, powerful engine that is easy to tune. The Super Tigre GS-45 and the Magnum XLS .46A are wonderful, powerful engines that might be only slightly more challenging to tune.

There literally isn't a bad .46-size engine for sale at Tower Hobbies. The Tower Hobbies .46 and the GMS .47 engines are a bit tricky to tune and require slightly longer break-in than the rest previously mentioned, but they are very good values with gobs of power. You won't regret buying the O.S. Max .46 AX by any means, but some of the less expensive choices are amazingly good as well.

You guys are a real big help. i really appreciate it!

I've been thinking, and realized i do not have enough room right now to build a kit as I am still stuck in my apartment for now, so are there any good ARF's you guys would recommend? maybe similar to the 4*40?

Also, I was looking at the 11x7 MAS Master Air Screw prop mentioned above and it says it's made exclusively made for electric flight. Is this a problem?

Get the non-electric version of the prop http://www2.towerhobbies.com/cgi-bin...&P=SM&I=LXZ972

The 4 star also comes as an ARF http://www2.towerhobbies.com/cgi-bin...&I=LXFKA9&P=ML
and also comes in yellow http://www2.towerhobbies.com/cgi-bin...&I=LXFKB0&P=ML