Pay deposit to owner for home purchase at a later date??

[Jordan Perryman]

Hello everyone, I purchased a home in the southside of Richmond, VA, which is a blue-collar area with cheap houses and decent rents. While I was renovating, the lady that owns the neighboring house approached me and said she was looking to sell. I don't have the 20% down currently, and when discussing sub2 she seemed uneasy, so we are trying to put an agreement in place that will allow me to purchase the house within a 1 year time frame for a set purchase price of $45k. I will pay her a deposit of $3000 (leaving $42k once we go to purchase), half of which will be refundable any time in that year if we decide to back out or can't get financing. In the mean time I will manage the property for her and we will split profits above the PITI until we purchase. She will be responsible for repair costs. What type of written document should we put together? What issues do you see with this type of transaction? I really appreciate any feedback you can give.