Once we pay off the mortgage. My husband wants to change the name of the deed to our son. How do we go about doing this?

You have to file a quit claim deed, deeding the property from you to your son.

But this will involve tax complications, because you are essentially gifting the house to your son. So there would be gift tax.

What is your purpose in doing this?

If your son is married, your daughter-in-law might be your landlord some day.
If the intemtion is to get rid of assets, bearin mind that Medicaid will check back on your financial transactions for 5 years back and penalize you.
These transfers are almost always a bad idea. Please talk to an elder care attorney before doing this.

My husband is 67 and wants to insure that the rest of the family will have a roof over their heads if he dies. I guess due to him being Middle Eastern, he does not think he can put it in my name. Our credit history is a little bad and he just wants to establish our son's and to protect the family.

A will will accomplish the same thing without incurring gift taxes.

Who would have to pay the gift tax? How is it calculated?

The person giving the gift is responsbile for the taxes.

What you might be able to do is "sell" him the house but forgive the maximum amount you can give as a gift without paying taxes for each year until the sale price is paid off.

My husband is 67 and wants to insure that the rest of the family will have a roof over thier heads if he dies...Our credit history is a little bad and he just wants to establish our son's and to protect the family.
You may want to consider an irrevocable trust. Trusts are a little complicated, but more efficient in yielding the desired result. You (and your husband) should consult with an attorney about estate planning.

My son is only 21 and will not be given a mortgage to buy the house. He just got a settlement on an accident and wants to help out his father.

He doesn't have to get a mortgage. YOU can give him a mortgage. He signs a promissory note agreeing to buy the house for a fair market value. You can then each gift him $12K a year (total of $24K) You do this each year until the sale price is paid off.

I thank you so much. I have to tell you that I am not on the mortgage or the deed. Only my husband is. So, would I still be able to do what you said? Can I also just sell him the house for what is left on the mortgage?

Doesn't matter that you aren't on the deed. You can both still gift him the max ($12K) each year. But the sale has to be for fair market value.

Fair Market Value is what the selling prices in my area are? Or, is it what the house is truly worth? How can I find the FMV of this house?

Ask a realtor in the area. It doesn't have to be exact, but if houses are selling for $300K and you charge your son $200K, the authorities will not like the transaction.