Well, do you know the story behind Septimius Severus' ascension?

The Emperor Pertinax was murdered by his own guardsmen, who promptly announced that they intended to sell the Empire to the highest bidder. While Pertinax was well regarded as an elder statesman, the man who would eventually succeed him, Didius Julianus, came to power by taking the Praetorians up on their offer and literally paid them an enormous bribe to proclaim him Emperor and enforce his rule in Rome. This earned him lasting infamy.

Severus was outraged, and declared himself Emperor, marching on Rome. Predictably, Didius Julianus' bribed Praetorians were no match for Severus' veteran legionaries and they gave him up for execution.

Afterwards, it was clear the existing Praetorian corps could not be trusted. Severus, in possession of Rome with a large army at his back, was in a position to dictate terms. He forcibly disbanded the Praetorians under the implicit threat of violence. Then he raised a new Praetorian Guard from amongst his own soldiers. I'm unaware of any financial incentive Severus may have offered to sweeten the deal, or what happened to the old guardsmen after disbandment.

Sorry for any oddness, posted from my phone.