ok, well she started off with her being able to pay 100 a month at least. so since she did that, she asked if it would be better as far as just taking it out of rent. BUT seeing as to how i will be making only one more payment of rent? how does that ensure the rest of my money? I will be moving away and have ways for her to get me the money, and seeing as to how she might be moving from the current place as well, how can she repay me for something neither of us live in?

This is why i need a contract, or something of the sort. i am moving and so is she, i need something for me to know that she will keep her word to paying 100 a month.