In consults with emerging artists I often hear that they want to know how to produce investment-grade art, the thought being that magically, over the course of 5-10 years, their art will increase in value. It does not work like that, unfortunately. When you start out as an artist your work does not have value other than the cost of your materials. It does not have a primary market yet, let alone a secondary market - investors, of course, being interested in the latter.
Do not be pressured into believing that you should produce art for the market. When you are starting out, your art is your future earnings potential. The best thing you can do is to develop your style, improve your technique and grow into your own identity as an artist. Furthermore, the only way that your art can increase in value is if it is substantiated by a successful career: solo and group exhibitions, critical acclaim by the art establishment, prizes, placement in museum collections and so on. Sales alone will not achieve that. The financial performance of your artworks is directly correlated to how successful your overall art career is. Taking this long-term approach will pay off years from now and will allow your potential to be turned into reality.
Finally, even though certain types of art can be viewed as assets (i.e. easily tradable Picasso’s or Warhols of a certain value) most collectors still buy an artwork because they love it.