Side hustles come with two big money-management challenges: They have to be funded, and you have to figure out what to do with the extra income you bring in. It's overwhelming.

On the side of my full-time job, I've continued my side hustle as a freelance writer, editor and book coach. That means money coming in from several clients -- in addition to my regular paycheck -- each month. Not a bad problem to face, but one that requires some hyper-organization to keep my personal finances in order!

If you have no idea where to start and need to get multiple streams of income in order, here are a few simple steps I've taken that I recommend you focus on first:

Open a new bank account for your new income.

If you keep at it, your side hustle could turn into a full-fledged business. Practice smart money management now so you're not scrambling to get organized when the cash is flowing in.

Even though my side hustle income belongs to me (not a separate business entity), I still keep it in a separate account. That lets me easily keep track of how much I bring in outside of my day job.

It also gives me a clearly defined pool to draw from when I need to spend money on growing the hustle, so I don't dip into my regular income. That gives me peace of mind knowing I'll never spend more on the side hustle than I make -- without putting much effort into accounting.

Your separate account can be as simple as a PayPal account, especially when you're small. It lets you invoice clients for free and get paid directly into the account using whatever payment method is convenient for them.

Be frugal to earn free time.

If you ever want to grow your side hustle into a main hustle, you'll need to eventually siphon hours from your day job -- which could mean a smaller paycheck. So you're not afraid of this eventuality, practice frugality now to get comfortable at a lower cost of living.

Don't worry. Saving money doesn't have to mean you live like a monk, as my Penny Hoarder colleague Mike Brassfield likes to say.

You can still enjoy life. But before you spend on something indulgent, put the cost into perspective: How many hours at your day job do you have to work to earn the money? It's an easy way to decide whether an expense is worth it.

Don't spend more than you make.

When you have a full-time income, it can be tempting to dump money into your side hustle and treat it like a hobby. But, as you might guess, this is a good way to ensure it never becomes much more than a hobby.

If you want to grow a sustainable hustle, treat it like a business. That means running lean as long as you can and making smart choices about what you spend money on. It also means, in my opinion, not using loans or credit card debt to support your side hustle.

"The only real business is a business that turns a profit," my colleague Jeff Haden wrote back in July of 2018, "and it's a lot harder to turn a profit when you're paying off debt you didn't need to incur."

Instead of taking on debt to grow in a hurry, keep your day job to cover necessities, and reinvest your side hustle earnings to grow that business carefully. That added security is the beauty of a side hustle.