I've only loaned out one male, and gave a female to a friend to be bred by one of his.
The male I loaned out was a breeding loan that I really didn't care what came of it. I just let him use my male but I don't want any babies. I was giving that male to my sister after I got him back anyway..
My big female on the other hand, means a lot to me. I let a breeder friend take her for a few months to be bred to a couple high end males but she didn't take. I took her back to do my own breeding this fall. The agreement was 50/50 split. If there happened to be an odd number of morphs, he said I could have the extra, but I wouldn't care either way.
Now there is the possibility of sperm retention since she locked multiple times all summer with his males. If I do still get a morph from his pairings, he will be informed and we'd still split whatever we could 50/50. If there was only one from his pairings, and the rest from my pairings, I'd just give it to him.
The point I'm making is you need to figure out what will be done in every scenario. There has to be trust between the two of you, and some give and take.
It's easier if your friend lives near you and is a well known and trusted friend.
Otherwise, you really need to document your agreement, what will be done in any scenario the clutch can provide. A contract of sorts is a great idea if you both are in it for gain.