Good news. The gift can be made tax-free. There is no income tax on a gift, either to the donor or the recipient.
There is gift tax; however every American gets a credit against federal Estate and Gift Taxes of $192,800 which is equivalent to transferring $625,000 tax-free. And, if the donor is married, the spouse (if an American) also can use the $625,000, so that your in-laws may, as a couple, give $1.2 million to you free of Estate or Gift Tax. The following link will bring you to the discussion of this exemption in the Free Advice material on Gift Tax:
https://law.freeadvice.com/tax_law/gift_tax_law/unified_estate_gift_tax.htm.
There is also an annual credit of $10,000 per donor for each gift given to each donee, so that your in-laws can give you and your wife $40,000 gift-tax free every year. What this means is that they will only use $152,000 ($192,800 less $40,000 ) of the lifetime exclusion.
However, be sure the transfer is a gift.