Donna Marie:
Here are my thoughts
Should I get an EIN now even though we're 3 weeks into the 2nd Quarter?
I believe everyone who is doing business should get an EIN. Especially those sole proprietors so that you never have to give your SSN out to anyone. The process is simple and can be done online a IRS.gov.
Are my taxes going to be a complete nightmare??
Depends on your tax situation, which is different for everyone. I would consult an accountant or tax professional.
Currently I plan to only have this one client, should I still start an LLC? About what will this cost me?
The LLC costs differ from state to state and again each person is different. I operate as a sole with a DBA and this works for me. Here is a great article on the difference..LLC vs Sole Proprietor