Choosing odds 2.00 and over, you just need to win at least 51% and you will be profitable, but if you go lower, like take odds 1.70 and below, you need to maintain more than 51% winning rate, I can't compute but it needs to be higher and its a tough job.
I agree that having a higher winrate is difficult to pull since the average odds of your bets is 1.7 but choosing lines with odds above 2.00 and at the same time maintaining a 51% win rate isn't much different because usually these are underdogs. I myself take bets above 2.00 but only on certain markets like 1x2 and european handicaps.
For professional sports gamblers, sport betting is like trading I think because of good analysis and correct predictions which are possible in sports betting unlike normal pure gambling that involves only luck! However even at the end there's always a possibility of twist. I guess the only difference between trading and sports betting is in trading if your prediction is wrong, you have the chance to rectify, but in sports betting, you lose all the funds!
Some sportsbook have a feature like cash out and similar to trading this prevents you from losing all of the amount you risked on a certain match.