Weekly pricing, help with structure of deal

I'm trying to structure a deal for my consultancy and would like the opinion of others about whether the following is a standard approach:

1. I'm thinking of doing billing weekly with bi-weekly reporting/feedback. Is that common?
2. When should I get paid? Should I do net15?
3. Does it make sense to have a price markup on components that I've already made for different projects in the past?
4. Is it standard to include a clause in the contract that I'm free to renegotiate/change the agreed fixed weekly pricing?