Ways to mantain a mount

Mounted combat is really cool part of D&D, but sustaining a mount seems like it would be difficult and costly. What are the rules governing the sustainment of a mount and are there ways for low level/poorer characters to do so? Also, are there alternatives to owning and maintaining a steed that will allow you to engage in mounted combat but not have to worry about keeping a horse during the long stretches when you are not traveling or fighting on horseback? For instance, Figurines or Power and Find Steed spells can provide a temporary, "disposable" mount. Are there other methods of doing so, magical or otherwise?