Unfortunately, if art is going to appreciate (and only 1% of it does appreciate), you'd have to own the painting another twenty to thirty years before it's actually worth anything more than the original invoice from the gallery. The law changed in the late 80's that the gallery offering a work of art cannot appraise that art -- some are dodging that by issuing a letter of estimated value a disavowing that it actually means anything, just what a like work is selling for today. However, that's in a gallery so there is a mark-up from the artist's selling price -- which drops down to about 30% of what you paid for it as soon as you walk out the door with the artwork. It might even be a large depreciation today until the economy improves, even though art auctions are faring well for old and modern masters. Proliferating a lot of prints does not help, contrary to popular belief. A Google search might show a broker or auction site like E Bay with the artist's paintings for sale.
Moral of the story: buy art because you love it and it looks great over your sofa -- do not buy it for investment. If you want to insure it, use the invoice price or an accredited appraiser. The bad news there is an accredited appraiser acceptable to an insurance company will charge you $ 500.00 or more for a document.
gives you some more information -- apparently from my search, there is nothing on E Bay.