Vesting: Yes, you should absolutely have vesting. Its very common for the founders shares to vest so that one guy doesn't do 2 weeks of work, leave, and come back 5 years later when its a success claiming that they own 25% of the company. You don't necessarily need to do the same one year cliff that you do for employees - I'd recommend vesting 1/48th of everyone's shares each month for four years. You should also add an acceleration clause that says you immediately vest your shares in the event of an acquisition (for a great primer on vesting and acceleration, check out Brad Feld's post)
Valuation: There's two ways to handle the valuation issue. If you're going to be raising a large amount of money early on and don't plan to raise any for a while you can do a standard raise where you value the company. However, if you just need to raise enough to get you through the first 6-12 months, a better method may be through convertible debt. In essence, the investors loan you the money (say 250K) but don't actually get the shares at that time. Their loan then converts when you do your series A round (usually with some sort of preferred structure where they get a 20% premium or so). Convertible debt is great for founders because it allows you to avoid putting a valuation on your company before you actually have value.
Convertible Debt vs. Pricing Your Round:
Mark Suster has a great post on the pros and cons of doing a priced round vs convertible debt. I'd highly recommend reading it and considering everything he talks about.
Pre-Nup Agreement As to the agreement: know that you aren't asking for anything crazy here. ANY startup founders should (and often do) talk about these kinds of issues before getting started. Any experienced lawyer should be able to help you draw up a partnership agreement between you and your partner that cover all of these issues (along with things you probably haven't thought of yet).
Corporate Structure Finally, you may want to speak to a lawyer about how you are planning on setting up the agreement - I know that here in the US, no credible investor will put money into an LLC (you can read this Answers.Onstartups post about it). You'll save yourself a big headache by setting up the company properly at the beginning and not having to convert it.