NEED HELP - Analyzing Potential Portfolio Purchase!

[Rosemarie Farnum]

After analyzing around 60 different properties and deals this month I think I have finally found one that could work for me. I've ran the numbers a few different ways and still come up good, however it is a Portfolio purchase comprised of 4 single family properties. I would be seller financing about 400 k after 60k cash DP at 5 percent amortized for 30 yrs. I have a cash reserve specifically for this purchase and would love hear from / personally talk to someone with experience to see if 1. I am overlooking anything 2. If there is a better way 3. Is it smart to make extra payments monthly to save on interest, and 4.Things I need to know about taking over a portfolio purchase . Mentors are welcome, thanks in advance!