Able to be covered?

You sound pretty level-headed, Stang V-8. Why not invest your cash or use it for college, and put off that Mustang for a few more years? There's no hurry.

Your original question about leasing. There are a lot of factors that go into a lease. You will have CAP costs which are equvilent to a down payment, you will need to pay first and last months lease, and a few other costs. In terms of what the car will be worth at the end of the contract is based on your negotiation at the begining of the contract. There are two options 1) closed lease and 2) open ended.
With a closed ended lease you will negotiate a final buy out price of the vehicle. At the end of the lease if you want to buy the vehicle that is the amount you pay. If you turn it back in you will owe for extra miles not pre-negotiated, any damage to the vehicle beyond normal wear etc...

Open ended leases are where the buy out price is not pre-determined and you will invariably get screwed on this deal. The leasor can simply say if you want the car, it will cost X amount.

The best advice if you are going to lease the car is to negotiate the price of the car with options as though you were going to buy it. Then inform the dealer that you are thinking of leasing and want to go that route. If they want to re-negotiate then walk and go to another dealer. When you lease a car the dealer will sell it to a leasing company and you will actually lease the car from them.
In order to get the most from it, know what you are paying for the vehicle, know what your milage limits are and cost of any additional miles (can be purchased in bulk at lease inception in some cases), final purchase price at lease end, any and all termination penalties etc . . .
As far as what your monthly payments are that will depend on your dad's credit, cap costs, length of lease etc . .
There is no real way to say what a monthly payment would be until you sit down with a sales person and negotiate