So Gate says:
"In the case of a single creature, you can control it if its HD does not exceed your caster level."
So if I can get my caster level up to 22 then I can summon a Solar using gate and control it without having to pay for it. This seems a little broken to me so am i interpreting the rules incorrectly or what? Thoughts.
Gate is a 9th level spell. They're mostly a little broken anyways.
That said, yes you can control a solar with it. Temporarily. And solars have buddies. Who might just take an interest in why you're calling General Aldebaran of the Celestial Host away from an important battle to squash kittens (or whatever).
Generally speaking, all of the outsider-calling spells rely very heavily on GM adjudication for balance and to work at all. My general theory is that you're usually much better off calling someone to do something they would want to do anyway. But, yeah, if you can boost your caster level to 22 (not at all difficult for a 17th level cleric; orange ioun stone and strand of prayer beads are the obvious way), you can have a solar around.
If you're not wise enough, or intelligent enough, to think through the issues very carefully, and address them beforehand, you deserve whatever your GM is going to do in return.
That's what it says, so that's what it is. You would first have to get your CL up to 22 of course which I assume is possible.
The trait gifted adept and allied spellcaster would do the trick as long as both of you have the feat and gate spell memorised. Plus the orange ioun stone mentioned by tonyz.