1) Web hosting and domain. Personally I use FatCow.com because their customer service is great (it's outsourced but they have online chat and fix things immediately) and they are pretty cheap. People trust sites that have a .com address with its own domain over anything else. You have more control over what you can post where, and more control over raising your web ratings. You even have more control over who can see your work - I don't allow mine to be pinned on Pinterest, and I can track who right click / downloads my images.
2) A web site creator (a human) or an HTML / CSS for dummies book / or a class - I took a class on Dreamweaver at the community college. Great investment!
3) A lawyer and an accountant. Nuf said. The lawyer is even more important if you photograph people - I also invested in a Business Law course and a Small Business Owners class at the college.
5) Backup for your images. Harddrive crashes are your worst enemy. I would recommend getting a Drobo or other form of backup for your precious photos.
6) Pay the fee to send your images to the US Copyright Office so you are protected from theft.
DON'T PAY FOR:
1) A payment card program / print sales site separate from yours - I use Storenvy to sell prints online instead of SmugMug because it's free! It's linked to my paypal account. There are also apps out there that you can use to sell your prints off your site but they may cost money. Some HTML geniuses can figure out how to do it - but I'm not one.
2) A business phone - I use Google Voice as a number for my business so I don't have to give out my cell number - for the same reason - It's free. I can organize calls into folders like Gmail. I can easily block numbers, and I can even record calls!
3) An online organizer program to track clients / sales / etc. I use Microsoft Access to track who ordered what when - what serial number print was sold to who when - etc. No need to pay extra money for something online.
4) A smartphone. (Unless you want to or do phone-ography or something.) Lots of people think they NEED a smart phone for their business. My answer is "why?" Clients can pay by credit card via Storenvy, and I don't need internet to finish a transaction with them. My portfolio is in my briefcase on shoots and not on my phone. I suppose some might find a reason they'll NEED a smart phone, but I don't lol.
5) Entry into contests!! Sometimes I joke about how I've never won a contest, but the main reason for that is that I rarely enter. Why? Well.... why the hell would I see it as a good business practice to PAY SOMEONE to consider my art? If my art is good enough to be seen in that way they should be PAYING ME to use it. Of course there are a few exceptions (a very few), but for the most part - if you're a pro photographer entry fees into contests are a waste most of the time!