Help required regarding the rules for contract Jobs (Urgent)

[ssm4u]

Hi,

I'm having a Tier 1 visa and I don't have any job for the last 2 months.
I've got a contract job offer which is going to work as follows.
I'm a contract employee for Org X which works for Org Y which is a big service provider and Org Y works for Org Z. According to my job profile, I'm going to work sit at Org Z's office to work.I need the following infos :
They are offering me $130-150 per day.

1. Is it safe to work in such situations as I've never worked as a contract emploee.
2. Who will pay me in this case.
3. How will I get paid and with what frequency.
4. What precautions do I need to take so that I can claim this earning for Tier 1 extension.
5. Is there anything which I need to know about a contract job.
6. Will I get any experience certificate for the contract jobs.
7. Will the company give me an appointment letter