What it will cost and how much you will make at an exterior, really is up to you. Things to consider when doing an exterior:
How much prep (scraping, sanding, and priming) is involved?
To what extent is Pressure washing needed? do you pressure wash the whole house, part of it or none of it? Is this before or after the prep? This depends on the quality you want to provide.
What warranty do they want in a product (quality of paint)? (varies in price)
What sheen do they want? (varies in price)
Ladders or scaffolding? That also depends on how you want to go about it... and how long will it take you using one or the other. each job is different. I don't bid jobs that need scaffolding any more. In the past, I would call a scaffolding company to give me a bid and include that cost in my proposal. I have never done an interior that justified the use of scaffolding either. Not that I wouldn't ever... It just hasn't happened yet.
1 lvl vs. 2 stories? I don't have this nailed down quite yet. To me, it comes down to time and materials.
What is involved in supplies? This again depends on how you want to attack the project. If you hand paint it, you won't need so much supplies compared to spraying.
Hand painting vs, praying. I did an exterior that took me 7 days to hand paint. It would have taken me 3 days to spray. The folks were dead-set on hand painting and payed the extra to get it done. Hand painting in my experience requires less paint. You can save on the cost of product that way. There is a local painter who only does hand painting in our area. Again, what do you want to do and how do you want to go about it? This will determine how your going to bid your job.
Labor (extra help outside of my capability to complete a job in a timely manner).... I don't use labor so I cannot vouch for this part of my bidding. It's just my partner and I.
I am sure I have only suggested a few surface issues in bidding an exterior.
Any other thoughts? I am sure to have missed something...