In order to successfully obtain an F-1 or M-1 student visa to the United States, you will need to show that your education will be fully financed and all your day-to-day living expenses (including for your spouse or children if they plan to come with you) will be paid without your having to work in the United States.
If you will be on an F-1 visa, your existing financial resources must clearly cover a 12-month academic term, and you must be prepared to prove that your further years of study will be covered as well. The government does not expect you to be able to pay for all your years of education the day you get your visa, but it will expect you to show where the money will come from.
If you will be on an M-1 visa, your resources must cover your entire 12-month (or shorter) study term.
If your family will not be coming with you, and you normally support them, you may also be asked how they will be supported while you are gone.
Your financing can come from your own resources or from support by family, friends, or scholarships. It can include personal funds, personal assets or property that is readily convertible to cash, or a scholarship or specified funds from other persons or organizations.
Although F-1 students are permitted to work during their student years under certain circumstances (usually at on-campus jobs or internships after the first academic year), you will not be allowed to rely on this type of work to prove your visa eligibility unless it is an on-campus graduate research or teaching position (usually called a "graduate assistantship") that is part of your academic program.
In fact, you probably will not find out until you get to the United States what type of work you will be able to get. The permitted work will probably be low-paying or a small part of your study program in any case—most likely a position in a place like the school cafeteria or library.
You will need to prove that your financial resources are real and reliable at the time you submit your application for a student visa. For instance, you might need to provide copies of recent bank statements, assets, and family employment.
Tuition alone (the fee to attend school) can be high in the United States, ranging from about $5,000 a year at public or state schools to $51,000 a year at prestigious private colleges or universities. Graduate and professional schools—even public ones—can be even more expensive.
You will probably want to look for sources of aid, such as scholarships, graduate assistantships, fellowships, or loans. International students cannot receive financial aid from sources supported by the U.S. government. That means that most schools, having few non-federal alternatives, cannot offer much financial aid directly to international students. Your school might, however, be able to help you locate other sources of aid.
Beware of services that offer to research possible scholarships for you at a cost. Many of them go to the same resources that are available to you for free—and some commit outright criminal frauds. For more information on the scams, see the U.S. Federal Trade Commission's website.
Some countries place a limit on the amount of money that you can take outside of it. The U.S. government is aware of these restrictions and will not grant you a visa if they don't think you'll be able to transfer sufficient funds to pay for your education. Talk to other foreign students or a lawyer in your home country to see whether there is a way to legally get around this.