Legal Guide on Buying/Selling a Mobile App

We are looking for a legal expert who can counsel us on 'drafting' or 'finding' a well written document online that we can use as a starting point to draft a sale agreement/contract for purchasing one or more mobile app(s) from Google Play Store. Some considerations in the Sale Agreement -We see the transfer of ownership of a mobile app as an asset sale rather than an equity sale. -Intellectual Property must be reassigned to the buyer of the mobile app by all those individuals and companies that may have contributed to the project. -We intend to use a third party website to 'escrow' funds while the transfer of ownership is finalized. We need to define whether there is a way to go back out from the agreement by either party, such as if the Intellectual property rights are not assigned to the buyer. -We want to be sure that the revenues of the mobile app initially provided by the seller , and used for the estimation of the value of the mobile app, are accurate and truthful and we need some provisions to guarantee this. -We may need to transfer existing contracts accounts set in place by the existing owner for receiving funds for advertising and other contracts set to generate revenue by the mobile app. -We don't want to be liable for anything the buyer might have done up to the date of the sale agreement, only after the purchase is finalized.