SalSterling

After submitting the application then there is option to submit any supporting documents that applicant wishes to provide and there your father in law can provide a simple letter to the consulate officer about this business, and supporting documents which proves that he owns that business, tax returns, bank statement for last 6 months. Most important is the purpose of his visit. If he is a successful and a busy businessman then he barely have 1 or 2 weeks to take off from his business and if he mentions he is going for few months then there will be more questions. Most businessmen get the B1/B2 by providing their on going relationship with their clients in US or if they are a client of a US business or going to attend a conference / exhibition in Vegas or wherever belongs to the industry applicant belongs and there must be some sort of registration with that conference to prove. Thank you.