
I can't provide you with a sample Contract as I've never entertained doing this, but as this could so easily get messy (friends or not at the moment), get anything you can think of that could go wrong covered in writing, and then think again!! Is she going to remain in your name because if so, as I imagine would be the case, the paperwork alone needs to be covered re getting her puppies KC registered.
She'd have to live up to expectations and then tested (who pays for that?).
Who keeps the litter, or which puppy (pick or otherwise)?
What if the worst happens and she dies in the attempt?
Who whelps and rears the puppies - where?
Who pays for any vet costs involved?
Who chooses the stud dog?
What happens if she fails any tests - if she's not transferred into your friend's name, will you do that so she remains a pet?
Using a Solicitor could become unnecessarily complicated (and you must use one who knows about dogs and breeding). Without an officially drawn up Contract (who pays for that), most Contracts drawn up between two non-qualified people are usually 'not worth the paper they are written on' I'm afraid. But it would show 'intent'.
I happen to think it might be less complicated if you kept your best bitch until she's of an age to be mated (and had all the tests necessary) and then once she's whelped and reared the litter, sell her to your friend.