Tourist visa after 1st rejection

[vijer]

My wife's brother along with his wife and 1 year old kid got rejected for his US visitor visa in New Delhi. He wasn't given any reason in writing but the officer interviewing him said that he was not convinced that he was going to leave his family business in India for 2 months. He had made a mistake of writing in the form that he was going to visit USA for 1-2 months, though he had planned to visit only for a month. He has a nice business in India that he manages with his father and Uncle. My question is if he should buy a ticket for USA for 3 weeks now before they go for a interview for a second time would that help and be good proof that they plan to go only for a limited time. From the websites I had read that buying tickets before getting a visa is not recommended. That's why I was confused what he can show as proof that he plans to only go and visit us for a short period.

Please advise. Thanks a lot

Vijay