One of the main advantage of a mirrorless system is to being mirrorless (sorry for the pun). Of course in an ideal world where we all rich, the best solution is to buy the top of the gamma lenses of the brand we have and then we are pretty much sorted, but for who just started into photography, or like me, where the mirrorless camera is more a lightweight alternative to the heavy duty DSLR we already own, and maybe we don't want to invest billions on a second system knowing that we already have spend plenty of money for the lenses for the big boy. But there is any cheap alternative? Of course there is, and you can find it in vintage lenses.
On ebay and similar sites, or even in most of the camera shops in your city, it's pretty easy to find old used lenses, sometimes even older than us, and most of the times, unless you are looking for rarities, they are extremely affordable.