I spent my professional career in business focusing on domestic and international finance. Because of this I became very aware of the need to understand business & finance basics if you want to turn your hobby into a business. So, whether you like it or not, you better brush up on your business skills or hire someone to do it for you.
Thought I would give you some "advice" on business topics I think are important. Not an all inclusive list but this will get you going. Remember "your results may vary" but I consider these boot camp basics,
If you are doing this professionally with expenses & income (payables & receivables) it is a good idea to get an LLC. This is more important if you have a studio space,
Don't borrow on plastic (can us debit cards), and if possible don't borrow at all. Debt repayments can force you to take jobs you don't want to take. And oh-my those interest rates on credit cards,
Track your expenses and keep your accounts up to date. It can be as sophisticated as an accounting software package or as simple as MS-Excel
Keep an inventory of all of your gear, and get it insured,
Keep track of your client's contact information. Get their contact information and stay in touch regularly,
Develop a pricing model. If you have more business than you can handle, first, good for you, but secondly increase your prices. It's ALWAYS easier to lower your prices than raise them. Be competitive, but don't lowball yourself,
Be an amazing communicator. Follow-up quickly. Be clear. Document your conversations,
No Drama. Don't let yourself or your business become a drama magnet. That extends to social media as well,
Remember who your customer is. Your customers is the person / entity that is paying your salary. Be polite & remember how you would like to be treated if you are a customer. But a also remember the customer is NOT always right, but they deserve your respect even if they are idiots (OK, that wasn't very polite).
And you noticed I didn't mention gear at all. There you go, free advice.