As the dance proceeds, keep an eye on the weather. Rain can wash freshly applied latex right off the wall, and a temperature dip below 50 degrees F two days after application can interfere with adhesion and curing and dull the sheen of glossy paints. (Latexes like Sherwin-Williams's Duration and Benjamin Moore's MoorGard Low Lustre are formulated to tolerate temps as low as 35 and 40 degrees, respectively.)
Prime. Dark colors, stains (once sealed), and previously unpainted surfaces (drywall, spackle, etc.) will need a primer coat, usually white. NOTE: most paint stores & home improvement centers will now tint primer (at no charge) to match fairly close to the color of the finished coat, that way two coats of primer need not be applied.[6] Although not all surfaces need a prime coat, skip this step at your peril! Dark colors will likely show through the first -- or even the first couple-- topcoats of paint. Sealants and unpainted surfaces like spackle patches will absorb or repel moisture in a topcoat at a different level than the areas surrounding them. Applying a good primer coat will help even out these differences. Primer equalizes a wall to a uniform surface. It's like erasing a canvas before drawing a new picture. Although some will argue the point, you generally don't need to spend a great deal on primer or buy special primer. A cheap, 5 gallon (18.9 L) bucket of plain, flat white paint will usually do the trick and cover a large area. Give your primer at least 24 hours to dry (follow its instructions) before applying a topcoat.
Compare offers. The painter offering the lowest rate may not always be the best painter for the job. Indeed, the total cost isn't the only factor to consider when choosing between multiple bids. You'll want to look at contracts side by side to ensure you're making an apples-to-apples comparison. Are the same materials being used? Are the same services included? Does the painter provide a warranty?
After you have done the multiplication, subtract about 40 sq feet per window, and about 60 sq feet per door. Divide by 400 (interior paint covers 400 sq feet per gallon). The number that remains, is how many gallons you will need. If doing multiple wall colors, then you should do this process for each room (or sets of rooms) with a particular color. 
Expect to pay between $600 to $3,500 or $1.25 to $3 per square foot to coat vinyl, with prices likely increasing for the finish. It is one of the more inexpensive siding materials to have repainted, especially with recent innovations in materials. Changing the finish on your siding is not recommended unless it's completely degraded and worn away by the weather. You can save nearly half the vinyl siding installation cost of $4 per square foot by painting rather than replacing. Before adding a new coat to vinyl siding, House Painting Denver Colorado