Can I claim against a guy who proposed to do business with me, took $4,000/- and doesnt want to pay me back?

I have met this guy at a mechanic shop, we exchanged numbers and became sort of friends. He then proposed to do a small business with m by buying damaged cars, and since he is a mechanic he will fix the cars and sell these cars and split the profit. We started by me giving him $4,000 to buy that 2001 Honda accord. He took the money from me and now is claiming that the money got stolen.
After a really bad argument, I took him and went to a lawyers office, prepared something sort of a contract agreement saying that I have lent him $4000 as a loan and to b e paid back to my over a period of 8 months at equal monthly installments of $500. This contract has been witnessed by a lawyer and notarized by a notary public.
If this guy default? What should I do?
If I go to court and claim against him having this contract as a support, and he tells the judge he has no money to pay me back, how do I get my money back?
Does he go to jail? Any help please!

The lawyer said that if the guy defaulted, he will be unable to take this case any further. He doesnt do that kind of cases, however, he said I can still go to court and file against him!! Lawyer was even too busy!

If the guy defaulted, file a case of garnishment so that his properties will be sold and the proceeds will be paid to you.

What does your Lawyer say on this?

Great Case for Judge Judy. You can take him to small claims court.