paint estimating

My neighbour would like his window trims, 3 doors and 3 garage doors painted in an oil base. He is willing to pay the "going rate" and I could use the extra $$. What is fare in pricing? By sq ft or time?

I have found that the per sg ft estimate that some have been giving is on the low side I have been told to estimate between 1.50-4.50 sq/ft. Anyone out there agree. I was told this is what the unions charge?

Is there anything I need to do to prep my kitchen from oilbase paint to water base paint ?

I'm trying to start my own business. I would like to know how to find the going rates on interior and exterior paint jobs in my area. Thanks, Travis