Mark Antony's signing bonus which he offers to Vorenus is the equivalent of ten year's salary, in advance.
Caesar is seen suffering from a seizure which Posca describes as "Morbus Comitialis", which at the time was seen as a curse from the Gods.
It is historically believed, but not agreed upon, that Caesar suffered from Epilepsy and this is such a seizure shown.
Julius Caesar's wanton spending is historically accurate. During his younger days, he actually fled Rome twice to evade his creditors.
Although most scholars believe Caesar suffered from epilepsy, other possible ailments include absence seizures or possibly hypoglycemia, which can induce fits similar to epilepsy.
Although being a slave seller was not a socially prestigious position in Ancient Rome, it was an extremely profitable one.