Zack, by now you should be seeing a pattern. if not here goes:
1. IP assignment clause. non-negotiable. the company must own the IP and unless you have an explicit IP assignment clause the company does not own the code/IP even if you pay him/her.
2. NDA - you just want to be sure everyone understands that you take your important business info seriously so s/he should too. if S/he quits and joins your biggest competitor you want grounds to take action if need be.
4. letter of understanding. I'm no attorney, but i've spent a lot of time working with them. I recommend that you hire an attorney TO REVIEW and FINALIZE the things you think are important, but draft them all yourself so you understand them. You can start with standard agreements from a number legalzoom-like sites. Too much legalese can get in the way of understanding and/or reaching agreement. I like to write up a letter of understanding that says in plain english what your expectations are and what you've discussed and when you discussed it and with whom. The attorney may or may not want to include it as an exhibit to the agreement.