If he was fully gelded, “studdy” behavior should fade away. If he was mishandled as a baby, he may be one of those young horses that the owners thought it was cute when he put his hooves on their shoulders. That may be a much bigger problem. Also, $800 I would be looking for injuries or an incomplete gelding from an undescended testicle or other odd medical issue. Since you asked this forum for feedback, I think your gut is telling you something is off. No matter what anyone says, it will be you making the decision and enjoying or not the consequences. If you get him, spend a great amount of time on groundwork. Expect him to bump, strike, kick, bite, hem you up in the stall and lean, territorial issues, rearing to put his hooves on your shoulders, not stopping when he runs to you in turnout. If he doesn’t do these things great. If he does, it may help you not get injured. Expect for someone to have tried to sit on him too young and taught him to flip or bolt or buck. Expect him not to stay tied and to set back in cross ties or single tie or flip. Expect him not to load and to scramble in the trailer. Train him as slow as molasses both establishing you are lead horse and trust-my dad said “enter the stall with a carrot in one hand and a doubled up lead rope in the other in case (she-abused young mare we could afford-became best kid horse ever) starts to kick.” It worked. Give him boundaries. This may be an over abundance of caution but if he doesn’t do these things then yea and if he does maybe you won’t get hurt. On the plus side, you said he was friendly and responsive so if his basic personality is good, it will shine through. Be very cautious about using gimmicks such as tie-downs, martingales, draw reins, too tight side reins. Some horses explode with these. I was warned off them as a kid-same mare, rearing. An old cowboy told me everyone would tell me to use them, they did, but that mare would fight until they broke and would have an uncontrolled flip. I listened to him. Listened to someone else about side reins as an older adult once on another mare and that old cowboy was right. Good luck with your decision.
Assuming you have the abilities to train an unstarted, essentially unhandled horse, I wouldn’t worry as much about the gelding. I bought a 4 year old unstarted stallion that had live bred a few mares, gelded him, started him under saddle and ended up selling him to the owner of the barn, who adored him. Was safe enough for his kids to ride, turned out with whoever. Less aggressive than some of the other geldings that had been gelded early. Be aware that there could be issues, possibly might try to mount mares if he is turned out with them, etc. But there is always a chance of issues popping up with any new horse. And of course, don’t hesitate to get help from a trainer if you get to a difficult spot, but I’m sure you already know that.
I have ridden and handled intact breeding stallions and recently gelded ones too.
It all depends on your abilities and their temperament. Many good stallions behave themselves when around mares/ geldings because they respect their handlers. Just like any other horse.
If this horse has been kept completely separated from other horses it is going to be hard to know what he may act like. The studs at our boarding barn were housed with the general population with geldings on each side ( or on an end) but they had interaction with other horses.
He sounds like he is worth looking into as long as you feel comfortable working with a stallion-- because he will still feel like one for a while and the behaviors he had when a stallion don’t go away just because he was gelded.
His desire to breed will hopefully go away( you never know) but any bad habits or lack of training, or past bad handling will not. I loved working with the" boys". I found them very responsive and in tune with me ( somewhat like a good mare).
