I keep tabs on all project related purchases, expenses, and an estimate on time I spend.
I am finding that if you take your original estimate, multiply by 4 and change the units, you are set. (Especially if you succumb to shipfitters...)
for example, "I think it will cost me $200 to freshen up the motor".... Multiply by 4 = $800. Then change the units = $8000. Same goes for time. I think I can replace that floor in 2 days. Multiply by 4 = 8 days, change the units = 8 weeks.
What do I know, I have 4 projects going simultaneously, one daughter starting driving, Two vehicles needing some mechanical attention, an SUV currently needing tires.....
I also keep track of fuel costs (makes me wish I lived next door to work)
Scott