If your plan allows loans, you may borrow 1/2 of your vested balance. You will have up to 58 months to repay it. There are residential loans you can take 10 yrs to pay back, but that is only for primary home PURCHASE. Not to pay off an existing mortgage. As long as you pay it back there is no penalty or tax, if you default or leave employement before it is paid back taxes and penalty will apply,. If you are able and you do borrow a large amount, they will deduct the payments (in most cases) right from your paycheck, the larger the loan, the larger the payment.

What if your money is not with your company and you want to borrow to pay the exsiting loan off and pay it back to yourself out of the 401K if it is with a credit union does the samething apply that you can only borrow if it is a first time buy, or can you borrow to pay your existing mortgage and have longer than 10 years or is it the same

Basically there are two types of loans from your 401.. a general purpose loan, 1/2 your balance up to 58 months to pay back.
The other is a residential loan.. up to 10 years.. but it MUST be for primary home purchase at the time of purchase. to pay off your existing mortgage your only option is the general purpose loan.