Loaned money to family member

What is the name of your state? Wisconsin
Our son wanted to buy our house and we wanted him to buy it. He did not have the 20% down-payment. So when he applied for the home loan we gave him the $20,000 (at 4% interest) with the VERBAL agreement that he would pay us back on a monthly bases. My husband always had the "best intentions" to have him and his wife sign a legal document saying we loaned the money and that they were to pay us back, but he did not. The bank "looked the other way" and as far as the bank was concerned we had gifted him the money. Our son has only paid us $1,300 in 3 years time. Is there any way we can force him to pay the money back on a regular monthly bases?
Thank you
[email]riley@athenet.net[/email]

[stephenk]

ask him to sign the loan document now. tell him you need it for tax purposes.

then if he doesnt pay on time, sue him.