Jean,
I use a little form I created to list all the repairs that need to be done:
roof
outside painting
replace kitchen
replace bathroom
windows
carpet
etc…
I add up all the items – let’s say there are 12 things. Then I multiply that by the square feet of the property. Let’s say it is 1200 sf – that equals $14,400 in repair costs
ta da — quick and easy
Now some things will cost more on the list and some things will cost less but it all balances out.
if the house is especially nasty, I will add $2000 for misc.
If it is a home in a more expensive neighborhood, I will double the repair costs because I will need to use a better quality of materials
try it