A short sale in Logan Utah / questions about offer price

[Ken Fricke]

I found a possible short sale deal, My Realtor says the ARV amount after renovation would be 140k he owes 115k. I am very new to real estate investing so pardon me if this question seem basic. I would like to flip the house so if i take 140k times .70 which equals 98k minus rehab costs of 25k that would equal 73k should that be my offer or should i also take into account Realtor commission and contingencies , I have done one other flip with a short sale not using this formula and made around 5k does not seem like enouph return on my investment for all the time and trouble and risk! I would like to do a successful flip on a short sale if possible. Any suggestions?