Definitely get a trainer to assess and get on the horse first. Do NOT buy a green, out of work, young horse as your first horse without very strong assurance from a competent trainer that the horse will be suitable.
Some horses are really sweet on the ground, but get on their back and put some pressure on them and they go off their rocker. I had one like that on lease that I ended up sending back to the own much to her disgust. He was a talented, well bred warmblood but put pressure on him and he'd stand up.
My coach actually only this week, purchased a potential new school horse. Rode it at the owners place, quiet as a lamb. Owner had the bit in it's mouth upside down and back to front and how was happy as larry!
Got it home, put it on the lunge, quiet as a lamb again, no worries. Got on its back, put her leg on and took up a small amount of contact. And it bucked so hard that all 4 legs came off the ground, and it was at least 5 feet in the air. Got the rider off and continued bucking through the arena getting 5-6 foot of air under it. It KNEW how to buck. Sweet as anything on the ground, but put a small amount of pressure on it, and off it went. It could have killed someone.
My current horse is an absolute sweet heart on the ground. He will stand for a cuddle for hours, fall asleep with his chin on your shoulder, no kick, bite etc. what so ever in him. But hell he can be spooky! He'll be going along beautifully under saddle, and suddenly something will worry him and he will leap violenty. He has bolted at one point as a result of this. But sweet as pie on the ground.
Don't get sucked in by sellers who can talk the talk. The proof is in the pudding, the horse is what it is, put it under some pressure, make sure someone gets on it before you buy it. Personally, I would never advise a first horse owner or beginner to purcahse an out of broke, green broken young horse. Until it has pressure placed on it, you will never know what it's brain is like. I'd be nervous that it is 7 and only green broke, and out of work for at least 12 months. Some alarm bells would be ringing.