Walking into debt?

I am worried. My brother-in-law requested my husband to be his guarantor for his scholarship to UK. In his agreement with the seminary, the tenure is eight years, otherwise, my brother-in-law is to pay back based on pro-rata calculation. I objected to this, but my husband obliged because he is his brother and he was very firm that he would complete the tenure.

However, in less than two years, they are sending their daughters back to Hong Kong. I believe very soon my sister-in-law will find reason to return, even before getting a job. Then, follow by my brother-in-law, who, to my opinion, does things following his instinct.

Proverbs 11:15 

He who puts up security for another will surely suffer, but whoever refuses to strike hands in pledge is safe." My brother-in-law asked me not to worry, he said he will not burden me. I do believe he does not want to burden me. However, he is a naive and also an ignorant person. How not to worry? He doesn't have an actual figure of how much to pay back, and how much does it cost to live in Hong Kong, at least how much he should have for his income if he were to work in Hong Kong, etc. When he doesn't even have facts and figures, how can I not be worried?  Grow up..... When they walk away from this country, am I and my husband walking into debt? God, open their hearts, to live realistically!