First I look at the condition of the home and note any repairs that are needed. If I'm doing the repairs then they are noted and added to the final painting bid.
Now, I count the windows and doors and note the type and condition. I also pay attention to the siding type and condition.
After talking with the home owner you should have a sense of the colors and amount of colors they want. Will the soffits be a different color than the siding and trim? What about the windows and screens? Also note the amount of accents and approximate colors desired.
You need to come up with a material and labor cost. How long will each step take you and what do you pay yourself (per day or per hour)? Plus, how much materials are needed to get it done.
Now that you have the major costs figured out, add gas and equipment costs. Equipment costs are anything you have to rent.
Add everything up then multiply by a profit percentage. The profit is the business operating budget and covers insurances, equipment repairs, vehicle costs and advertising. I work within a 15% budget. This amount works for me, but might be different for your area.
You will have too use your own experience to come up with the overall costs of painting this home.