How to structure a fair deal for seller financing

[Eric S.]

Hi, I've recently became aware of a family member wanting to sell a property no longer being needed. I'm able to pull out equity from my home which would be around 20% of the value of the property being sold. I'm interested in buying it as an investment property but would not be able to be approved for another mortgage after I take out the down payment from my equity. So I would need to set up a payment program for seller financing if my relatives were even interested in doing this. Could you please let me know what would be the most fair way of doing this? Also, what is the best option/strategy for pulling out equity for this?

Thanks