Stripping – $54–$151/100 sq. ft.. “The principle of paint strippers is penetration of the paint film by the molecules of the active ingredient, causing its swelling; this volume increase causes internal strains, which, together with the weakening of the layer's adhesion to the underlying surface, leads to separation of the layer of the paint from the substrate.”— Wikipedia. All the stripper will do is soften the paint. You’ll still have to scrub or scrape it off.
Prep work should include removing all loose paint, either with a pressure washer or by scraping; removing any trace of mildew using bleach and water or a commercial solution, and sealing or covering dark stains; caulking all seams, corners and around windows or trim; applying epoxy filler to repair serious woodwork problems; covering dark stains; sanding all rough surfaces, and priming the bare wood with a bonding primer.
Some paints are two-in-one paint and primer products, or so-called "self-priming paints." These paints are designed to seal and cover surfaces in one coat. But, here's the secret: though it's called a paint-and-primer-in-one product, there's actually no primer in the mix—what you're really working with is just a thicker paint that often doesn't perform as well as using separate primer and paint.
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. 
When determining the total cost of a home’s exterior project, you’ll want to include things like the trim, a garage, foundation, windows and doors. All work is calculated by square footage and sometimes by the linear foot, such as in the case of trim. Your contractor will give you a price for the entire project unless you specifically ask for each item separately.

While vinyl siding salespeople claim it never needs to be painted, it does lose its color strength over time, and the degree of fading can vary depending on which sides get the most exposure to sunlight. Perhaps it still hasn’t faded, but you don’t like the color much. You can’t go any darker than its current color, though, because the siding is designed to absorb only so much heat, and a darker color could cause it to buckle. Vinyl paint is available in many colors. Brush painting and roll painting vinyl siding costs $43 per 100 sq. ft., and spray painting costs $34 per 100 sq. ft.

Painting exterior windows depend on the size of the window and the number of panes. To calculate the price for windows larger than 15 sq. ft., add 1’ to each side of the window and then multiply width x length. Add two sq. ft. for each window pane for painting the mullions, muntins, and sash and then multiply your total sq. ft. by $84/100 sq. ft. So a 4’ x 4’ window with 4 panes will come to a total of 44 sq. ft. x $84/100 sq. ft. = $37.
Your contractor will sweep or scrub the concrete first with a dry brush, and then clean it thoroughly with trisodium phosphate (TSP) and warm water, then let it dry. TSP is a mostly alkaline solution that does a great job cleaning grease and oil off concrete surfaces. Brush painting concrete siding costs $138 per 100 sq. ft., roll painting costs $50 per 100 sq. ft., and spray painting $32 per 100 sq. ft.
Homeowners report that painting a home’s exterior costs an average of $2,923 with a typical range between $1,734 and $4,119. The average price per square foot ranges from $0.50 to $3.50 depending on your location, condition of your exterior and accessibility. Stucco and brick cost an average of $1 per square foot more than vinyl or wood. The average 2,500 square feet home costs an average of $4,000, though it can range from $1,250 to $8,750.