A simple letter making an agreement with ex partner

I need a letter of just a few lines stating than when our property sells (we have just accepted an offer) that all monies after fees will be split 50/50 and also that I do not require any future maintenance from him. I require this to enable the sale to proceed. I have taken legal advice and realise that i'm going against what they advise, however this is what i am choosing to do. I would be happy to sign a disclaimer stating that I have gone against recommendations.