Do you think that for a sufficient price you could hire a dragon to fight for the Free Peoples? Of course, that price would probably exceed the amount of wealth in the known world, but hypothetically speaking...
Not if it couldn't be paid if it's boss was dead. That would be the hard part, though. You'd have to have a ridiculous amount of security, probably more than the fighting capability of a dragon would be worth.
Hold said reward over his head until you're about to die anyway, then try to fight him and you become a legend for standing up to a treacherous dragon.
On the other hand, I don't think that Smaug would willingly submit to Sauron unless he thought he was getting something out of it. For one thing, I don't think the dragon would leave his hoard unguarded. And he might not want to serve a master ever again. Smaug would have to at least think that he was being approached as an equal.
Dragons are greedy creatures. Even if they accepted your offer, they'd probably double their asking price after doing your dirty work.
Realistically, you'd probably get eaten before you made your offer. As someone once said:
Do not meddle in the affairs of dragons, for you are crunchy and taste good with ketchup.
I mean, Cad Bane was able to be dealt with...
Sorry, I'm not familiar with that one.
A Star Wars bounty hunter whose favorite phrase after encountering an inconvenience is "I'll be doubling my charge."
Hypothetically, you could try to hire a Middle-earth dragon, but could you ever really trust it?
Not if it couldn't be paid if it's boss was dead. That would be the hard part, though. You'd have to have a ridiculous amount of security, probably more than the fighting capability of a dragon would be worth.
It would never work because as soon as he gets the reward, he’ll barbecue you!
Hold said reward over his head until you're about to die anyway, then try to fight him and you become a legend for standing up to a treacherous dragon.
If you have to die, die with honour!
What if Sauron paid Smaug so much that he couldn't refuse? After Lake-town, Rohan would be next.
As Gandalf hints, I don't think Sauron would have had to pay Smaug.
On the other hand, I don't think that Smaug would willingly submit to Sauron unless he thought he was getting something out of it. For one thing, I don't think the dragon would leave his hoard unguarded. And he might not want to serve a master ever again. Smaug would have to at least think that he was being approached as an equal.