Hey Bubba,

If you decide to build a 40 sized DF from scratch (that is put the kit together, install engine, etc...) you will most likely spend the same as buying a used-good condition .90 sized jet.

I believe Jet Hangar Hobbies is what you are looking for in the .40 size range. I think the only good .40 sized DF engine left is the OS. There are more options when it comes to .90's (but only one is really-really good).

I saw recently a post for a BVM Agressor RTF for $900. At that price, you can't go wrong. If your budget is less than that then Electric Ducted Fans (EDF's) may suit you better. I recommend buying a second hand DF to get the feel for the jet, and you can learn how things are installed, and then fly the hell out of it. If you crash it, just replace the airframe. Remember that these kits used to be gold 10 years ago.

This is the time to buy DF