On the professional golf tour, how are caddies paid? Flat rate? percent of winnings? Tip money?

It depends. Caddies are not part of a union nor are they employees of the PGA Tour (for tax purposes they're independent contractors). What this means is that there is no set contract for payouts. Having said that, in talking with two former PGA Tour caddies and a couple people who cover the tour, a typical arrangement goes like this:

-A set fee for the week, regardless of finish. A good ballpark would be around (all figures US dollars) $1000-$1500 for the week depending on the ranking, the relationship, and the player's status. Tour rookies, Monday qualifiers are paying less. A-list players like Day, McIlroy, DJ, Mickelson, etc. pay more.

-A small percentage of winnings for making the cut (2-3%), which would include a MDF (events when the Tour has a secondary cut after the third round).

-Percentages go up for top-30/top-20, top-10, and wins. A good ballpark figure is typically a caddie would get 10% of prize money for a win (so if a pro wins $1.5mm for a win, his caddie would get 10% of that, or $150,000).

Keep in mind that both the player and caddie have to pay taxes on that, plus all travel costs (players have to pay their own travel costs out of hand which includes airfare and lodging; caddies work the same). Some caddies will room together as a group (often 4-5 in a room) while some players will let their caddie room with them.

Keep in mind that the player and caddie both pay travel costs even if they miss the cut and go home empty handed.

The player does, however, get the free use of a courtesy car at events and will typically give his/her caddie a ride to the course. Players also have access to a free buffet in the clubhouse; caddies treatment varies by event.

Frequency of payment is not set in stone. Some players settle up every week, others will settle up every two weeks, and some once a month.

Keep in mind that a player will often practice after a round (caddie will be there for that) in addition to warming up for tournaments along with practice rounds). In short, it's a 7 day work week if the player makes the cut. Player bags (the staff bags), weigh around 30-35 pounds after you factor in clubs, umbrella, rain gear, and all the other gear a player will have in their bag.