Well, you're not getting much input.

I can give some input.

Have you decided what you want to do: local only, remote only, support other preparers until you're better up to speed, find only a handful of people/businesses that will keep you plenty busy, only focus on Enterprise Funds and Not For Profits?

Have you joined, for example, Chamber of Commerce or other local business groups? Are you listed for your State's "whatever" listing that apply? For example, a new person in my town wants to work independently, so I pointed out how the State's vendor system works, and she can apply for bid and no-bid contracts, just like I was a vendor to the State for teaching and rehab, for job shadowing (veteran hires, for example) as well as I had a couple dozen of the towns and villages and special purpose districts as my clients (typically to get their accounting on track, prep for year end, prep for audits and grant administration). You know, the usual "need multiple jobs to survive" strategies.

I don't know if you consider this the type of business where people just cruise the web, and SEO may not really apply. Knowing what you want to focus on, or at the least, where you want this to end up, will help you avoid spending unnecessary time and expense. I had a client who paid a fortune to set up a website, etc, and then called me, she was lying on the couch still in her pajamas, crying, because it had been a couple of weeks and no one was calling. I got her out there, they're not going to accidentally find you. Get networking. She had two kids and wanted the flexibility but some steady contracts, for baseline income year round. She's a QB ProAdvisor and an EA and focused on retail.

You know you want an EIN to avoid giving out your SSN, and the same concept applies to business email. You want to cut it loose when you stop working, and don't mix personal with business. You don't need something fancy or even your own domain, unless your plan is to grow this company. For instance, I worked with some architects for 10 years, we went from 2.5 people to 22 people in 3 locations, and you bet we had our own domain (and custom email accounts), because it served as a point of contact and a portfolio. But another advantage of finding a domain and parking at the least on intro page, would be to accept secure/encrypted FTP for your clients, so as you research GoDaddy or whoever, consider what else they provide and support.

Payment methods are tricky. I would ask some small business people in your area (non-retail) who they use, and try to find someone doing about the same number of transactions as you anticipate. It might be as simply as Square and ACH. Which means an isolated business checking account solely for this, and treat it like a sweep account. That reduces your exposure to fraud.

And you'll want a risk prevention review for fraud, identity theft, systems security, etc.