I don't think it can be done. Take a look at the Wednesday tennis picks and the 90% of them were losers ( Karlovic, Melzer, Ginepri, Hanescu, Minar, etc ). And that happens most of the time.
Now I'd like to know about these other methods where you can reliably increase your bank without having to pick winners and get a liability on your bank in the first place? When people picked Karlovic they had to risk more than 5 times their stake for 1 part of profit. Picking underdogs doesn't seem to work either. You can study a match all you like and be 100% sure that it's a winner and it can still lose.
The very idea that you can use that as a reliable income to replace a job is ludicrous. It's gambling, you risk your money everytime you place a bet, so what are those trusted capping methods that work everytime?
You're really coming at this the wrong way and to say "it can't be done" is just plain wrong. For a few years I was doing it, before I lost my discipline, and work with and around people who have done it and are still doing it. Those who stopped did so because they came into positions that enabled to earn a very good living at less risk, but still in the gaming industry.
People who are good at capping their sport and sensible with their stakes are the people who have "trusted capping methods that work everytime". And if by "everytime" you meant every bet, then that's not what I meant. I'm talking on an annual basis.
Using some random week in the tennis world involving some very topsy turvy players to claim that it's too difficult is ludicrous. And you go on to say picking dogs doesn't work either! So picking favs and dogs is no good you say? lol. Well one or the other has to win, mate, even if you were just taking a stab in the dark.
People do do it, and as Dave said, the general consensus is that the % is two percent. So yes, for many, many people it is not a viable career choice, even if they actually know their sport well - as if they don't keep to all the other disciplines, they will fall. I can speak of that from personal reckless experience.
And when you say "be 100% sure it is a winner" is just something professionals don't deal in. A professional asseses match up and price and bets accordingly, they don't "know" for certain it will be a winner, but they are backing their judgement against the books and if they are as good as they need to be then they can and will make a living out of it over the long haul.
That doesn't mean a life of luxury, for some it may, but not all. Depends just what the stakes are, and there are professionals in all of the major sports, including tennis. There isn't a sport that is "easy" to cap and there isn't one that is just too difficult for anyone to achieve. Personally I always thought NBA or MLB were the hardest to conquer because of the day in, day out battles and the varying factors such as pitcher, but I ended up meeting people who capped those sports for a living successfully and in turn they couldn't understand how to conquer sports I was working on.
No sport is uncappable, but it takes a certain kind of person and quality to do it over a prolonged period. There aren't many of those around and that's why there are bookmakers in the first place. Alot easier to be a bookie than to be a bookie basher. Having played both sides of the fence, again I can speak with experience.
More challenging to be a bookie basher, but more rewarding to be on the book's side than not.