Part of this depends on what your plan is with the company. If you intend to seek VC funding, vesting is going to be renegotiated. Will your co-founder even agree to that?

I am concerned because vesting immediately is way outside of the norm. What stops him from walking off the next day?

A one-year vesting schedule is not advisable either. Are you really going to have a liquidity event in a year? If that's the concern, have acceleration terms to deal with that. I agree with rogerkirkness that 4 year vesting is the right way to go. I don't think 5 is necessary, though you can do that.

You can avoid the "boss-employee" vibe by having the same vesting schedule for yourself.

Trust me - I see a lot of bad co-founder situations. You don't want to have a co-founder with tons of equity who isn't working out.