First let me say your horse is beautiful. 

Second after years for standing stallions I know wouldn't even think about breeding for less than $1000 stud fee. It's just not worth your time & risk to your stallion. As of this last spring we stopped breeding to outside mares. Talk to a couple of people who stand stallions to outside mares and see if it's really something you want to do, if so sit down and figure what you think your stallion is worth stud fee wise then figure in your time and any other cost you will have, 

Good luck whatever you decide