I was wondering how many main/ significant characters can be introduced in one chapter or scene before it becomes "too many" for the readers to keep track of. All five of my important characters are introduced over the course of the first 5,000 words and while I don't want to waste time spacing out their entrances, I also don't want to overwhelm readers with a wave of names and faces.
Five doesn't sound too bad in theory but the challenge there is making their entrances interesting, memorable, and relevant to their scenes. The film Reservoir Dogs opens with every single major character (there are half a dozen if not more of them) talking with each other in a diner, yet Tarantino is able to convey how distinct their personalities are while also leaving some mystery. Amazing opening that is easy to understand but really has quite a lot going on character-wise. I'm really not sure how many is too many, but I wouldn't worry much about it.
There's no hard and fast rule (wouldn't it be easier if there more often was!), but if they're different enough characters, I wouldn't stress over it. Keep in mind too that a character can be present in a scene and not expanded on much - a proper introduction to who they are can always come a little later.
I noticed that if the story flows naturally, characters will come in when they are supposed to. If an introduction feels rushed or forced, it usually is. Something I did was also 'half-introduce' characters. Let their name be mentioned or have them only be seen from a distance, that way the actual introduction is less 'new'.
There is no magic number, as you probably expect. What is important, EVERY time you introduce a character—wherever this happens—is that the character sticks with the reader. That means you need more than a name and a potted biography. They need to do something that will make the reader take notice of them and remember them. This is not a time to whiz along with your story. Take time to get the reader oriented. Not taking the time to do this is a beginning writer's common mistake. In the haste to get the story moving, everybody gets named, maybe even superficially described. However, very few of these characters stick. Then, later on, when the reader wonders who these people are, the writer points to where they got a mention way back when, and says, 'but I told you who they were on the first page.' Give each new character enough story time and gravitas to sink in. If you can't do this, try to keep from naming them and let their presence evolve, as needed. Sometimes only a beta reader can tell you if you've succeeded or failed at this trick. If an attentive beta doesn't remember a character, then you need to do more to make them memorable. In general, though, keep the numbers AND names down.
5k words is plenty of time to introduce all five. Characters tend to jive in group dynamics anyway--they almost become one character when they share the page, like a family of four that follows a common orbit--so once you establish everyone's place you shouldn't have any trouble tossing them together. I guess if all five are in separate places following separate plots it might become more problematic. Are they all separate POV characters? That might be annoying as hell. A lot of it will depend on the story. If there's a lot of whiz-bang action with the characters facing common enemies/dangers you'll have more room for the characters to dance without needing tedious exposition to justify their existence. But if it's a slower or more multifaceted plot with lots of moving parts and disparate locations, your flow might need a defibrillator.