Using the equipment option to generate a character, they start flat broke. If I want to start the campaign with the standard "meet each other at an inn" trope, they can't even afford a meatball. Suggestions for starting coin here?

You could allow them to trade in starting equipment at the listed price before the game begins.

Though I'm curious what backgrounds they're taking, I wasn't aware that there were any that don't start you out with 10-20GP with your starting equipment.

There are some that only give 5, and I think that some campaign specific ones don't give gold (seems like the Haunted One from Curse of Strahd doesn't).

 For clarification, do you mean when creating a character on DnDBeyond? When creating your character, under the equipment tab and starting equipment section, you can choose equipment or gold. In this circumstance, the Outlander background will still give you "a pouch containing 10 gp" on top of the other automatic starting gear whereas the Haunted One does not give starting gold when choosing equipment in this way.

Yeah, in DnDBeyond. I notice some characters start with money & some don't. I guess I can just give everyone a gold or 2 to start off — didn't realize some start with money when choosing Equipment instead of gold. Would it be because of the lifestyle they chose?

 Or does lifestyle negate the need to worry about the cost of inns, etc.? Looks like I need to read up on that.

I'm not well-read on the topic, but I was under the assumption that all backgrounds (save Haunted One, apparently, and maybe some others) start you off with at least some gold when you choose Equipment over Gold in the character builder.

So, I would first ask - did all your players make that choice yet? You can tell if they don't because it'll have the choice in their equipment tab.

If they chose Gold rather than Equipment, then they have to put in what they rolled for gold and it will give them that amount.

As for lifestyle, that has to be taken out manually, as the character sheet doesn't track in-game time. So, no, their choice of lifestyle wouldn't have any effect on their current gold unless they took it out themselves.

These are characters that I created or I was sitting there walking them through the process. Not sure why it didn't give them money. I'll just add it manually from the background list where it gives the amount.

I think it would be a good start. "Hey guys, I'm flat broke, we need to find...."

*CRASH* a bloody townsperson flies through the tavern window landing on your table, scattering your ale and biscuits! What do you do?

This may or may not be acceptable, but before I started my homebrew, I had my players roll a given dice then multiplied the results by 10 and then the total was their starting gold. The given dice was determined based on their backstory. 

For instance, one of my player's backstory is that his family is the royal family of the made-up town that player is from. Since his family is royalty, one would imagine that his family sent him with at least some decent amount of money. So I had him roll a d10 and multiplied what he rolled by 10. He ended up with 70 gold. 

As others have said, most backgrounds give starting gold as part of their equipment packages.

With my play group, we also allow selling any starting equipment for full gold value before the game begins.

If you're the DM there's no reason you can't just give your players extra starting gold. You have the freedom to bend the rules to enhance the game, that's the magic of D&D. 

I use a homebrew mechanic - which I'm almost positive that I stole from somewhere, but I can't remember where - I call Wealth Levels.

Essentially - I give Characters a free Modest Lifestyle "wealth level". Anything that they could reasonably expect to afford as part of that lifestyle, we don't mechanically track money-wise. They don't pay for everyday meals, or a mug of ale at the Inn, or a simple or common room on the road. They can maintain their equipment. All of this is automatic.

They still need to pay for items that fall out of their Wealth Level - e.g. fine weapons, improved armor, stays in high-end Inns, buying rounds of drinks for the entire tavern, passage on a ship - these would fall outside a Modest Wealth Level, so they need to have extra coin for that.

Conversely, it is assumed that they automatically collect and sell equipment from intelligent foes, and any-and-all minor coinage - and that this all essentially disappears from the game and is assumed to fuel their current Wealth Level. For that reason I only tell them about notable items, gemstones, magic items, and high denomination coinage in treasure. It's assumed that all the "small change" just goes into maintaining their wealth level. 

They can upgrade their Wealth Level by paying 10 years worth of the difference out of "extra cash" - e.g. moving from a Modest Wealth level to a Comfortable Wealth level would cost 3,650 g.p. - while upgrading to a Wealthy Wealth Level would cost 10,950 g.p, and jumping to Aristocratic would cost 36,500 g.p. They can also downgrade to create ready cash for some large venture, if they so wish. 

This basically removes any minor fiddling accounting from the game - unless it's relevant to the storyline, or sufficiently dramatic. 

Under this setup, starting money doesn't really mean much to my Player's Characters, since they can still survive day-to-day, even if they have no extra money on paper.

That's a pretty good idea. I have groups that are almost polar opposites regarding loot. One groups loots EVERYTHING and the other doesn't loot anything so they sometimes end up short.