Payment/accreditation
NO money has ever been lost to one of the few schools that are accredited like a college or university, and those are the only schools now allowed to have the F1 visa. Apparently the US government is considering a requirement for all visas (M1, etc) to be given only to accredited schools. The requirements for that are very strict and severely enforced. If everyone just limited their search to accredited schools this thread would never exist. This is the most important thing you can do.
As to paying up front, don't pay everything but, these are schools with set and very high expenses. Some pay over $100,000 per month just for insurance. Most non accredited schools don't have insurance, and this is something else people don't check out! They need to have a decent cash flow to exist and also to keep their prices as low as possible. I understand why they can't allow "pay as you go." Just get a contract, WITH AN ACCREDITED school and pay over 10 or 12 months. Make sure that is understood before you commit to the school and you will have no problems.
They can't run their school efficiently and at lower cost if they have to finance your training too.