What about gulbis?
Ernests' Dad is a very successful businessmen and has stated that he wouldn't be able to play tennis if it weren't for his father's help in paying for a lot of the expenses, but wants to make his own money. His Dad's father was a professional basketball player as well and I would assume would make a fair amount of money. His Mum is an actress so I would assume the whole family is well off. In regards to Djokovic I heard he hasn't come from a wealthy family but I am not too sure. And Tomic is very wealthy so I have heard. However, as tennis is a fairly expensive sport to play with the cost of racquets, court hire, coaches, physio all the players would be fairly well off unless they received support from their country.