For whatever it is worth, in California, I needed a business license from the city (and probably would in most cities and counties in the state). I also needed a "home occupation" permit because I work from my home (simple bit of additional paperwork, since I don't generate traffic or manufacture anything or the like), an add-on to the business license. I got the license when all I intended to do was editing and related services, but it was simple to add on publishing when I started doing that (on a very small scale) last year.
Because I am selling taxable things (books) directly, I need a California seller's permit, and have to collect and remit sales tax. (I did not need the seller's permit during the years when all I offered was nontaxable services.) MD has a sales tax, and presumably pretty similar requirements.
I joined my local chamber of commerce very early on (shortly after I started the business), but I doubt that would be useful for what you propose. But it might be if your audience is local business people.
I use my own name in the business, and nothing else that triggers a fictitious name permit requirement. If I were, say, SuperDooper Publishing, I'd need the fictitious name permit, which would require some paperwork, a fee to the county, and the expense of publishing notice in a suitable newspaper.
I bought some business cards (nothing fancy), but don't bother with letterhead (I print what I need on my inkjet).
I have bought pens with business name as promotional handouts (probably not something useful for you, and not particularly useful for me, either).
Business income and expenses are reported on Schedule C, along with the rest of your tax return. If you keep careful, accurate records, then you should have no difficulty, whether you do your own or have your taxes done by a tax service or accountant. However, you should learn the ins and outs. For example:
http://www.irs.gov/businesses/small/article/0,,id=109807,00.html
http://www.smallbusinessadvocate.com/small-business-articles/beware-of-the-hobby-loss-rule-2023
http://www.irs.gov/publications/p535/ch01.html
Note the rules about deducting losses. There are some catches. And of course some kinds of deductions are audit triggers (home office deduction being a biggie).
If I were you, I'd chat with folks at the local SCORE office (you can track one down via
www.score.org to help you get organized and to figure out what you need to do. Chances are, it is pretty similar in MD to what is required in CA. But not necessarily.
Thousands and thousands, if not millions, of folks run small businesses as sole proprietorships. You might want to get a book on starting a small business (Nolo Press publishes such books) and read about the ins and outs and options.
--Ken