In my country we have one breed that no one gelds ever, because they are so docile- so first it depends on what kind of horse you're getting.
Nice, docile ungelded males do exist, I've seen more than one used as school horses for beginners. They where very reliable. So you can look specifically for a very calm horse. I'm not sure if you can get beginners' horses out of males who have already "known" a mare.
If you decide to buy and geld, please stay on horses under the age of five-six. After that age, you should geld only if necessary for medical condition. You'll hear of horses who did well after being gelded after 16 or so, but you never know, some horses actually do fine, some others develop health problems, some others stay with the "stallion" mind, some lose every vitality. So you'd have a very high chance of not getting what you want, either from horse not changing a bit, to horse changing too much.