2, an agent will charge 3% for the first $18000 and then 2.5%
3, to offer a price which is very closed to bank's value
4, subjuct to finance
5, subjuct to building and pest inspections
For the old house it may has some problem and then you can ask your friend to fix the problem or you can negotiate the sell's price to cover this issue.
Private sell will save both your money and your friend's money. Good luck!