If you are looking to buy art as a financial investment, then you should try buying stocks instead. Most reputable dealers in fine art are at least aware of the "potential" investment factor of a work of art, but there's no secret formula or "insider knowledge" as to what future prices for a piece of art will be. It all depends on many factors, most of which are quite unpredictable as artists' popularity and demand rise and fall and sometimes rise again.
Reputable dealers can and will often give you their informed opinion, but that is all it is: an opinion! There are of course, works of art that are always "on the rise," such as works by the masters or very well-established (often dead) artists, but when buying work by contemporary, living artists, the key rule should still be to buy what you like, and avoid anyone that suggests that you should buy it as an "investment."
We do represent artists whose work we think will rise substantially in price in the future, and have a certain "track" record to suggest that. Nonetheless, it is an opinion and an educated guess at best.