Section 1701j-3(b)(3) says:In the exercise of its option under a due-on-sale clause, a lender is encouraged to permit an assumption of a real property loan at the existing contract rate or at a rate which is at or below the average between the contract and market rates, and nothing in this section shall be interpreted to prohibit any such assumption.That means would you lenders please go easy on the borrowers.

I'd rather loose the vacation home... and be safe in my free and clear primary home. this does not take into account numbers and interest rates etc, just an exercise in the feeling of comfort. 

Exercise Science degree...nothing to do with getting into REI.

Homeowner shall exercise this right of access in a reasonable manner.11.Rental Rate and Fees: a.Deposit: A deposit of $500.00 is due upon reservation of the property. b.The deposit is for security and shall be refunded within 30 days of the Checkout Date provided no deductions are made due to: i.damage to the property or furnishings;ii.missing property or furnishings;iii.dirt or other mess requiring excessive cleaning (failure to follow check out procedure); or iv.any other cost incurred by Homeowner due to damage to property during Guest’s stay.c.The deposit will be held in an account until disbursement.d.If the premises appear dirty or damaged upon check-in, Guest shall inform Homeowner immediately. e.Rental Rate: Payment in full is due no later than 14 days prior to the check-in date.

Your dad could take a mortgage and then a couple of months in transfer ownership to you.There is a tiny chance that the bank will call in the loan when ownership is transferred but from everything I've ever heard, as long as the new owner keeps on paying the mortgage, banks don't seem to exercise this option.You'll not have to be qualified by the lender when ownership is assigned to you.

@Austin Fruechting said it well... like people know they should eat healthy and exercise, yet how many people really place it as a high priority in their daily lifestyle?

If you do the exercise please let me know what your numbers produce.  

They should be most able in ensuring that you know what your rights are and assist you in exercising those rights.

RSUs for example are taxed when vested whereas options are not taxed until exercised.

You could lease option the house from them, and exercise the option at a later date.