Contractors Responsibility

I wanted to get views on what responsibilities a contractor has to their subcontracted worker as well as a couple other issues.

1.) In my case I'm a programmer and I get programming work contracted to myself. The person who is handing me the work in some cases isn't the person who is in direct contact with the end client. They are actually having work contracted to them as well.

I'm running into a problem where they wont take responsibility in paying me promptly (30 day 'grace' period) because the people they are going through haven't paid them.

Normally I would hold whoever I am going through responsible regardless, but I wanted to see what the normal is since things may be different.

2.) Regardless I think I need to start witting up a contract for each project, and I believe this contractor would be for the person who is giving work to me. Not the people they are going through or the end client.

3.) What would be a reasonable policy to use for deliquent payment or non payments? I'm a little flexible, but have a family I'm supporting just by myself. I imagine a percentage late fee would be best, but not sure what percentage would be reasonable.

Feedback would be much appreciate.