Since you propose to run it on class I rails, you're going to have to pay for a pilot employee (e.g., an engineer or conductor who knows the route over which you propose to travel) or crew, and you should figure you'll need a new pilot crew every 100 to 150 miles. Your crews will also be subject to the hours of service law, so you will need two or three crews for each 24 hour period. And you're going to have to have insurance coverage, too. If you train derails because of a condition under your control, you will be responsible for the damages. I'd expect the damage policy would have to be in the 10 to 50 million dollar range. And you'll need liability coverage for yourself, and anyone else in your control, as the railroad will insist on being provided waiver of responsibility. In other words, if they break it, you still own it. You'll also have to pay to have periodic inspections and maintenance done on your locomotive(s) and cars, as I doubt that any class I will allow you close to their rails without current inspections.
Low end round numbers: $500,000, or more for the train; $500,000 a year for the crew; $1,000,000 a year for operating expenses (fuel oil, lubricating oil, rust preventative for cooling water, wheels, couplers, brake shoes, &c.) $500,000 a year for insurance coverage; 1,000,000 a year for trackage rights payments, $100,000 for the first year for pilot crews (assuming after that, your crews will be qualified and no longer require pilots).
So, I'd say from the low end, figure on 3.5 to 5 million dollars to start from scratch.
These are just guesses, though, and if I were pressed, I'd say they could well be higher, maybe much higher.
ns