I have doubts about whether you can do the required maintenance on a 35+ year old Falcon for 300K per year let alone pay other DOCs and fixed costs for 100-150 hours in a two pilot jet. If he is serious about the 450Kt min, look into an older Premier. You'll probably still be well North of the 300K operating budget, but you'll be a lot closer than you would be with an old Falcon 10.
The reality is the budget your owner is suggesting is not realistic for the parameters he's giving you. If you want to do him a service, get Conklin and Dedecker numbers and put together a realistic budget, or better yet, suggest a more suitable airplane. It sounds to me like he'd be better served with a King Air or more appropriately, an older Pilatus.
And, just FYI, there is no way a Falcon 10 ever catches a Citation X at 370 under any circumstances short of an engine failure. You're always going to be pulling the TLA's back soon after leveling at FL370 in a X, or you will quickly be blowing through the M.92 Mmo. Either you don't know the difference between a X and an XLS, or you're playing it a little loose with that story.
Excellent post. Far better than my gibberish. Even if the fictional guy in the story does take delivery this year (or has the FA-10 under contract this year and takes delivery next) and get the bound depreciation, how much tax savings are really there? On a 1M dollar falcon (happiest day in someone's life when they unload theirs) you get what? A 50% bonus depreciation this year? So you spend 1MM plus pre buy plus the 300K (which would mean a DOC of 2K/h @150 Hours) plus training and of course the OP's wage. So guy spends 1.5 to save 500k in tax and is now saddled with a rapidly depreciating jet on a calendar inspection schedule. I didn't learn much at "Silver Airways" but the numbers don't seem to add up.