Newbie in need of guidance

[Tom Killingsworth]

My sister and I recently rehabbed and sold our family home and caught the "flipper bug". We decided to partner up and formed an LLC in Phoenix, AZ to buy and flip houses. We will be purchasing the properties and our builder will be responsible for labor and materials on a 50/50 profit split. We have already vetted this builder and he is more or less a friend (but we know this is a business).

I have read here on BP that many investors started this way, so I am hoping someone could help me with basic contract or contractor agreement.  If you have a template that I could "borrow", that would be even better. 

I am concerned about the following 2 points:

1. If house doesn't sell and we decide to rent it out after a period of time, the builder is out his costs for labor and material.  What is fair? How should we write that into the contract?

2. Since we are funding the property purchase, who has final say on scope of work and needed improvements?  I am not anticipating a problem here as I think that should be ironed out before you buy, but you never know.

I welcome any other guidance/comments any of you can provide.  

Thanks!