Well, a ducat was worth anywhere from 80 to 500 USD depending on your source. I would wager closer to the 500 rather than the 80 so Vivaldi could have been paid anywhere from 35,000 to 50,000 a year in modern USD. However he paid almost a third of that to rent his home in Venice.
Antonio Vivaldi was buried in Venice where he was born. Antonio Vivaldi was buried in Vienna where he died on 28 July 1741. Alone and destitute, Vivaldi succumbed to a heart attack and was buried, that same day, in an unmarked grave at Vienna's Spitaller Gottsacker.