There are a number of threads/posts that we see here on occasion, that claim they have not been paid by some fly by night outfit. My best advice to anyone seeking work as a sub contractor is that you must do your homework.
Which includes but not limited to;
know who the prime contractor's owner(s) is/are, meet them in person if possible,
know how long the prime has been in business,
know their pay history to subcontracts,
know what is in the contract,
know who the owner of the project is and their requirements.
Further, do not take a lowball priced job with the promise of future higher paying jobs. They rarely happen. Do not work beyond your agreed pay period without getting paid. You will be only deeper in debt. A good prime has the ability to pay the subcontractors on time before being paid by the owner of the project. If they dont have that ability, you dont want to work for them.
Make sure you visit the job site before accepting a project. What is said on phone calls, texts, emails may not be what you actually interpreted.
Finally, please don't jump into a project because you are desperate, things usually will not turn out well for you. Make sure everything is favorable to your well being BEFORE you start the project. As I have said before, you will be much better off and money ahead, to stay at home doing nothing, than it is to work your a__ off and not get paid.