Horse is Very Stubborn, Help?

I just inheiritted a 23 year old quarter horse stallion. He's very calm and is halter broken. I'm very new to horse owning as I inheiritted him from a close family friend of ours who passed away recently.

So... the trouble we're having includes: he won't take a bit (he won't even open his mouth at all... completely clinched shut) and he stops in the middle of training and just stares at me. Those are the biggest issues that I notice... I'm brand new at this and I don't know how to correct it... I'm not sure how much training he recieved before I got him... and I don't know where I should start. There's only one decent trainer in town and she charges $400 a month (which I can't afford). ANY help that I can get would be greatly appreciated!!!

OK ABOUT TAKING THE BIT: put the bit between his lips and push gently (it might take a while). If that dosent work than place the bit between his lips and in the corners of his lips stick your finger in. They don't have teeth right there so it pretty safe. He should open and just quickly and carefully put the bit in. :)

If he was used only for breeding he has no idea of what you want. Many stallions are only handled with a halter and are not saddle or bridle trained. Are you sure he's a stallion? If so you might want to talk to a vet about getting him gelded. Stallions, even the very gentlest ones, have been known to turn on people. I hope it was just an error in terms and that he's a gelding. (neutered male horse)

Right now I wouldn't even worry about a bit. Let him adjust and start working on trust and respect from the ground. Hard to know without details of the training why he squared up on you but in the round pen you want them to face you and you want them to focus on you. Or is he being dominant? More info will help us better help you

Is he broke?
With starting a 23 year old Stallion, I'm worried about you and the horse. He is not young anymore and stallions can be very unpredictable, what kind of condition is he in?