Sharing of water for a neighbor's drilling & fracking operations -- any tips?

Our McMullen County Oil & Gas lessee has asked us for permission to use our deep water well (and our frac tank, I assume) to drill and frac our neighbor's property. Has anyone else ever run into this? Any tips (including current water price info) as to what might go into our side-agreement with the oil company would be helpful. (We want to be a good drilling partner -- and a good neighbor -- but we're leery of having our own drilling program consequently delayed and we're concerned as to where the neighbor's recovered frac water and fluids will eventually be going.) Any helpful tips will be gladly received....