I've seen it go both ways and both carry risks. If you loan out your female, there are obviously all the risks involved with her reproductive health but you also have to consider that some people are just dishonest and may not return her to you when you want her back or not return her at all. When you loan out a male, there's a bit of a risk involved that many people don't consider. If you're loaning out a male, what's to stop them from using him with additional females without your consent/knowledge? What happens if an animal becomes sick, injured or lost? Just some things to consider and work into loan agreement paperwork.
Breeding loans can be very rewarding and it's fun to share the excitement over a clutch with your loan partner, but if you're going to go into a loan agreement with someone it needs to be someone that you TRUST 100%. You need to trust in their ethics as well as their husbandry. If you are unsure or are getting any red flags when working out an agreement, don't do it. Better to be safe than sorry, especially when it involves your animals.