A clv betting strategy checks the work from the other side. Closing line value compares the price that a bettor actually took with the final price before the event starts. Beating the closing line again and again is the most reliable sign that a bettor's estimates are good, since the closing price gathers everything the market learned. Losing bets taken above the close are still good bets by that yardstick.
How does value betting work across a season? Small positive edges add up only over hundreds of bets, and variance hides them for a long time. How to find value bets in sports betting comes down to knowing a market better than the price does: a narrow league, a player's fitness, a line that moved late. Lines on the biggest events are the sharpest, and value there is small and rare.
Is value betting profitable? For a few careful and patient bettors, modestly and slowly, and for most, it never shows up at all. Is value betting legal? It is simply betting, legal wherever betting is, though books may limit or close accounts that win steadily. That limit is the real ceiling on value betting: an edge that the book notices tends to lose the stake size it needs to count.