Creating an addendum to a Purchase Sale Agreement

[Nick Talarico]

My wife and I are buying a duplex directly from a seller without an agent. This our first time buying a house this way and we are curious how you go about writing an addendum. We had the home inspection and negotiated the repairs that needed to be made by the seller verbally. In order to protect ourselves and ensure the repairs are done correctly and professionally we feel like we should put it in writing. 

Looking for advice in how to write this properly, is their a legal template available? 

What have other investors done to ensure the seller follows through with repairs and closing goes smoothly?

Thank you for your help!