@Ralphy Rosado The forms that we use in our markets are tailored to us. Not one form/ contract fits all if that makes sense. You will want to either grab a template from a pier in your hometown or go to a REIA club and start inquiring to see the proper forms for your area Rochester, NY. For the most part they are all similar however due to legal gobbledygook you want to be careful you are protecting yourself and the note holder against the piece of property.
Obtain PITI on the property, Principal, Interest, Taxes & insurance calculate the total payment that needs to be made per month. You will also need get a very good understanding of what type of loan is against the property as well: FIXED, ADJ, when does it adjust. Determine repairs as well as the Market rent against the PITI with rehab costs to see if you have a good cash flow rental on your hands.
For us the key to this strategy is explaining in such away to sellers how this strategy can really benefit them verse us. I have spooked off a ton of sellers with this approach because you need to educate in such a way to where you are adding value to them not just taking their home. Because remember they are essentially giving you their home (or cash for keys) and leaving the note in place so you need to make them really really trust you and have the sellers best interest in mind when using this.
Hope this helps!