buyer asked me to hold the note...how does this work?

[Robert Hastings]

my brother and i purchased a property last year for 40k.  we have a church interested and we named our price, 69k.  they asked me if i could hold the note and they would pay 1500/month over the next 48 months.  that would pay a total of 72k.  my brother and i would like to move foward with this.  ideally we would like one check as a traditional transaction, but the idea of 1500 month cash flow doesnt turn us off.  

how does this work?  in this set up, myself and my brother would be the "bank" im guessing, does that mean we have to sign the deed over before we collect payments, similar how buyers receive deed to property after settlement?!  what id they default after two years?  what if they pay on time, after the 48/month we just shake hands and walk away?! we really want to do this but not sure how to structure the deal to protect us.  i know most will recommend an attorney (which we plan on doing) but i wanted to do some research from the BP forum first so im not completely ignorant when we take this project to the next step.  any help would be appreciated.