I can try and answer some questions for you,but I'm sure there are more knowledgable Members on this Forum that will give more accurate info.
I reckon a player ranked under 150 on the ATP should make between $5000 and $8000 month,if he's lucky.
As far as Im aware no Tournaments supply free Hotel Accomodation,Travel expenses,or food.
The Grand Slams provide something like $300 expenses money a day to any player who makes the Main Draw.....Wimbledon about 200 Pounds a day.
Most Pros will get their equipment and clothing free of charge from the sponsors.....even potential 12 year olds in America are sponsored with equipment and clothing.
Im sure some of the Top Players recieve appearance money.....but not a Million Dollars a Tournament like Tiger does.
The top Juniors and future potential Pros in America recieve a lot of help from the USTA......that I know as a fact.
Other countries Im sure do the same.
About taxation on prize money.....you'll have to ask Steffi and Boris about that.
...just kidding I love Steffi and Boris.
So when you turning Pro.?
You want my advice....learn to play Golf. 8)