How to structure a deal to buy properties from parents

[John Fassnacht]

Hello all!  First time poster here looking for some advice.  A little background information on the situation.  My parents have been small real estate investors for years with ~12 SFHs.  They have always self-managed these properties but are now looking to retire and shed many or all of the properties.  I have a rented out my first home for 6 years so I have some experience and I am thinking about expanding my investment activities.  This provides an opportunity for me to acquire a few of their properties but I am concerned about how to structure the deal so that it's a win-win for both of us since I obviously do not want to damage my relationship in the hunt for the best deal etc.

Why this deal makes sense:

1. They would be willing to seller finance for a low interest rate & down payment since I'm not a risk and they don't need the money immediately.
2. I can cherry pick from their properties to get the 3-4 that make the most sense for me.  I have direct knowledge of all the properties and their histories including rents/costs.
3. Direct sale so no relator/mortgage fees.

Any advice on how to structure this to be fair to both sides?  I think there are enough benefits for me that I don't have to have the best deal considering what I will gain from the inside knowledge and financing.  My thought was that we agree on a discount rate from an appraisal value.  Then get all the properties appraised and if the numbers work out on my side I buy the ones I want at that price.

Does this plan make sense?  What should the discount rate be?  I was thinking 15% or 20%.  Any other ideas on how to structure this?

Thanks!