If you need loans for the exam, I’ll suggest you not to appear in the exam at all. Because passing USMLE Step 1 means nothing unless you go to USA for two months’ electives, which will easily cost you few lakhs depending on the location.
Passing USMLE is just one of the requirements. It doesn’t guarantee you’ll get residency in USA. So, unless you’ve enough money to spare without lamenting over it later, don’t go for USMLE at all. From appearing in the exam to getting residency. entire process is very very costly for an Indian.