Would a judgement against them (the husband and the employed wife) prevent purchase of another house etc with this judgement against them?
Maybe. It would hurt their credit score so they might have to come up with a larger down payment to qualify for a mortgage, and they would have to pay a higher interest rate than someone with good credit. The interest rates they pay on any credit cards or new auto loans would be higher as well.
Credit scores are also used to calculate your insurance score, and a low insurance score = higher insurance premiums.
Of course, if the bank forecloses on their house then they won't care about their credit score.
If the wife is still working and you get a judgement against her then garnishing her wages also becomes an option, unless she files bankruptcy.
Overall, how badly a court judgement hurts them depends on whether they really are having money issues or whether they are scammers who told your friend a sob story to get $11k out of him.