most of our (family's) companies are set up as DBAs. There's one LLC (for business that sells food product). Every area varies as to what to file for DBA's. Where I'm at, there's virtually no paperwork, just have to file with State Tax Commission to get Resale Tax Permit and tell the bank that you want to open a checking account as a DBA (not required, but handy for business expenses and income, esp. when it comes tax time and dealing with the IRS). If lived 3 miles down the road, would have to be registered with city.
As you've probably figured out, there's various advantages to each type of business, just depending on your needs.