However, the fact of the matter is, that this is a sticky situation for a couple of reasons.
1) You do not have a boarding contract in writing. You need to get one.
2) When you get a contract in writing, you will then have a specific day set forth on which your board is due. And, you can also specify what will happen if you do not pay on time. (This is the same concept as if you have an apartment and your rent is due.)
3) You don't have to not give him money until you have all of it. While I agree with the others that late is late, why not as least give him part of your board money that you do have now? Then at least he has something and it shows that you are making an effort to pay.
I would have to side on your boarder on this one. He's providing a paid service to you. And he expects to be paid. While I don't think it's fair to the horse that he's not feeding it (if that's truly the case), he can certainly hold the horse against you if you do not pay. Andn there's really nothing you can do about it, especially since you have nothing in writing.
Have you gotten receipts in the past from him when you have paid board? If you do not, and he would ever decide to sue you for "months of board you did not pay", you would be SOL in the eyes of the court.
I know it's nice to be able to trust people, but with society being so "sue happy" and no one ever getting anything in writing, it's a law suit waiting to happen.
Get a boarding contract in writing and get boarding reciepts from him!
And maybe pick up a second job if you are struggling to pay your board from one incident where you got some cash stolen. I know its hard to save money (I"m goingn through the exact same thing right now), but it is really important.