Dallekainlo Saan dai is right But I would say, since you have assistantship you don't have to worry about making any papers back in Nepal for your wife and son. Just collect some money from your friends deposit in your account here in US, get a bank statement with sufficient money. You may need your own money for their health insurance because the International student office will not issue I-20 until you deposit some money for their health insurance and this is refundable in case the visa is denied. Apply for F2 I-20 for your wife and your son, return your friends' money. Send I-20, ask to apply for F2. Let your wife know not to slip from her mouth that she is going to live for a long time but just until your study. They will definitely get visa. Don't let your beautiful days spent without your wife and son. Its really good to be with the family. Best of luck. I would be glad to know when your family gets visa. I hope this is helpful to you.