You may be able to borrow money from your 401(k), depending on your plan's rules. If you do so, you may have up to 10 years to pay the money back, since you are borrowing it to purchase a home.

One caution with borrowing from your 401(k) - if you change jobs, either voluntarily or involuntarily, you may be required to pay the loan back within 30 - 90 days or risk having the loan become a premature distribution. If this occurs, and you are under 59.5, you will pay federal income tax plus a 10% penalty. Some states also charge income tax and penalties. So check with your plan to determine if this is true.

The same tax and penalty situation applies to withdrawing (rather than borrowing from) a 401(k) plan, so that's not a good option. You will probably end up with, at most, 65% of the money that you withdrew, after taxes and penalties. So it's usually better to borrow more money against the house instead of withdrawing from your 401(k) plan.

For the Roth IRA, you can withdraw contributions to the plan at any time. So if you put $20k in over the past 5 years and the account is worth $30k now, you could withdraw up to $20k with no taxes or penalties.

If your Roth IRA has some money that was converted from another IRA or a 401(k), and the Roth IRA account is at least 5 years old, you can withdraw the converted amounts without taxes or penalties.

If you are a first time homebuyer, you can also withdraw up to $10k in gains without penalties, but you will have to pay taxes on the money.

Any withdrawals from retirement accounts are permanent. You cannot put the money back into your account after you sell the house. If you take a loan from a 401(k) plan, you will need to pay back the money, or it will become a distribution.