A wand of cure light wounds can substitute for a healer, but it's risky to adventure without someone who can also heal
A wand of cure light wounds costs 750 gp, making it beyond the means of a party of newly created level 1 characters. Nonetheless, this answer assumes the party gets such a wand anyway from, like, a friendly squirrel or whatever. This answer also assumes the party doesn't immediately sell the wand, split the 375 gp 4 ways, each spend 1 gp per day for 3 months living large, then start adventuring for real without the wand. (I can imagine some players deciding not to use such a crutch.) In short, let's say the party both gets and keeps the wand.
If in-combat healing isn't a concern—and, most of the time, it shouldn't be: PCs overcome challenges by breaking foes not by repairing each other—a wand of cure light wounds that can be activated consistently is a fine substitute for a dedicated PC or NPC healer. That is, assuming a party of 4 level 1 PCs has a collective hp total of about 45 and an encounter exhausts 25% of that, a single wand of cure light wounds used after the encounter depletes only 3 or 4 of charges. It's possible a lone wand of cure light wounds could last such a party the entirety of its first level and three or four encounters of its second.
(Keep in mind that such a party—unless it includes wizards or other weak, imperceptive, ugly characters—needn't worry about resting. Their healing dependent upon total charges rather than a creature with limits due to class and level, that party may continue adventuring long after most other parties would've been forced to stop and rest. This might be a concern for the GM as the party may overadventure, exhausting the GM's material. Such a party should then expect to fight an aasimar then an aballonian then an aboleth…)
However, consistency is key. A party of 4 level 1 rogues with one wand of cure light wounds between them and all trained in the skill Use Magic Device—however unlikely—can all fail Use Magic Device skill checks by rolling natural 1s and be unable to heal for the day. (By the way, when one of those rogues makes a Use Magic Device skill check, rolls a 1, and fails the check, he can hand off the wand to another rogue to try it; the 1-and-a-failure doesn't wreck the wand for the day but wrecks that rogue's ability to use the wand for the day: "[I]f you ever roll a natural 1 while attempting to activate an item and you fail, then you can't try to activate that item again for 24 hours." Emphasis mine.)
This possibility of horrible failure makes it almost a necessity that at least one PC have the spell cure light wounds on his spell list so that activating the wand isn't an issue. That such classes include bard, druid, hunter, inquisitor, paladin, and ranger (and many more) means it's likely at least one PC—maybe even accidentally—has a spell list that includes on it cure light wounds. That makes that PC the default after-action healer.
But I wouldn't put my character's life exclusively in the hands of a level 1 rogue with a wand of cure light wounds acting as the party healer unless he somehow managed to get his Use Magic Device skill check modifier with wands to +19. Seriously, a potion of cure light wounds is only 50 gp (thrice and a third more than a charge from the wand), and resting is free.
By the way, the Use Magic Device skill says, "You cannot take 10 with this skill," but that's debatable. However, taking 20—unless success is already assured—is right out: "Since taking 20 assumes that your character will fail many times before succeeding, your character would automatically incur any penalties for failure before he or she could complete the task" like rolling a 1, failing, and not being able to try to use the device anymore that day.