well that all depends. There are alot of texture resources online that are royalty free, but most of them are just a base texture and alot of them aren’t all that great.
If you took your time and made nice, high res textures that were straight (alot of times with photographs, they’ll tend to be slightly skewed/turned because of the angle the photo was taken) and included normal map/bump map layer via photoshop, you’d probably make some decent $$$
probably even more so if you actually created material libraries (it’ll hold all the texture info… size, scale, tiling, specularity, bump, diffuse, ect) in 3dsmax and exported them for sale.