Painting a house is not hard, depending on the house.
-Before you paint, test for lead. If you have lead, you will probably want to get a pro unless you have experience working with lead (and you'll have to check local laws - in some areas, this may be illegal...and if you have lead and decide to tackle it yourself DO NOT SAND!!!).
-In that vein, make sure you do not have an asbestos shingle house. If this is the case, consider abatement, but at minimum hire a pro who is licensed in working with asbestos.
-What kind of paint is there already? Are you sure it's paint? Many homes have solid stain in place (stain won't peel and soaks into the wood, although some solid stains an be "scratched out" of the surface). If there is high gloss paint on the home, or you are trying to paint with a semi-transparent stain, hire a pro. Seriously. If you DIY these wrong, it will cost you many more thousands to correct. You cannot paint a lower gloss paint over a higher gloss paint, and many primers will not bond properly to the sheen of a high gloss paint underneath.
If it's a standard two story home with clapboard siding, that's a fairly easy job. Assuming you have above ground power lines, you need a 24 foot fiberglass extension ladder and a 6 foot fiberglass stepladder. The fiberglass is non conductive when working around power lines (don't get aluminum) and these ladders are both extremely useful. The main advantage of aluminum is low cost & light weight, but if you're trying to keep equipment purchases to a minimum, just get these two ladders. Be careful when working around power lines - many local utilities you can call them and they will wrap your power lines for free as a safety precaution if you tell them you are painting. If you have a half basement, you will need a 32 foot fiberglass extension ladder to reach the upper levels and eaves of the home from the side of the home where the basement is above ground level. Taller houses, you may need a 40 foot ladder, this stretches the limits of what one person can do by themselves as these ladders are extremely heavy.
Always put ladders at as close to a 4 to 1 ratio as you can (4 feet up for every 1 foot the bottom of the ladder is away from the home), on level footing. There are devices you can buy to level a ladder, do not rely on rocks or other random things to stabilize a ladder. It's best to raise an extension ladder with two people, but it can be done with one fairly easily, and not unsafely...just choose a good spot to do it (hint: on level ground near your home, but far away from power lines).
It's a good idea to gently wash the home with a mixture of bleach and TSP substitute (unless you live in a state where you can still get actual TSP). A hand pump sprayer is cheap and will do the job for this one, just be sure to rinse it out with water afterwards as the bleach is corrosive to the typically copper lines these sprayers use. This will kill any mold or mildew before you really start working. Rinse with water to clean the surface and let it dry for a couple days. Then scrape any loose or peeling paint and sand if the prep spot is now uneven (unless you have lead paint). Spot prime with a good latex primer. The paint store can tint your primer to be similar to your finish coat (avoid exact match, as it will make it hard to eyeball what has and has not been finish coated). Take down and label any downspouts or shutters, so you have access to everything on the outside of the home.
When you purchase paint, make sure you purchase primers and finish coats for the same purpose from the same company. These products will be specially formulated to bond with each other, and the paint store rep can advise you on the best combinations of products to use based on the material. You will have to use different products on different substrates, so if you are painting any masonry (basement foundations, stucco, etc.) you will need a different paint for this part than for your siding and eaves. The paint store color matching can ensure the colors of both products match each other (if that's the look you're going for)
For recommended sheens:
-For siding or foundations get flat or eggshell
-For trim use satin
-For entry doors use semi gloss or high gloss, depending on the look you want. Entry doors are the absolute hardest to paint, and if you're not comfortable doing this, you can hire a painter, and reduce your cost significantly by doing the rest of the house yourself. The key with entry doors is avoiding brush marks and paint drips, which isn't always easy.
If you have a deck, and it has not been previously painted, stain it. Seriously. Painting decks, sucks. The paint always peels off. Use a stain specifically formulated for a deck. However, if it was painted last time, you're stuck painting unless you want to pay to have everything removed. If your deck is new and the wood was pressure treated, wait at least a year to stain it until the wood has gone through a winter.
While you paint, also make sure you fix any substrate defects you may encounter - recaulk failing bead around windows and doors to close gaps, and if you have wooden windows, fix the glazing if it's falling apart between the mullions on the exterior, or along the edge of the window sash where it meets the glass. You'll need window glazing, and a small putty knife for this, and a caulk gun and some caulk. If you want to paint the caulk, make sure you get a paintable caulk (not silicone). Silicone is more durable, but you can't paint it, so be aware of this if your trim color is vastly different from the caulk color (typically silicone is a semitransparent cloudy white).
Once that's done, you're ready to finish coat. Fair word of warning though - if you are changing color, it will typically take two coats to cover. The cost of a sprayer is not typically worth it, as the paint adheres best when you brush and roll to "get it in there" so if you're DIYing it, just brush and roll. Make sure you get all surfaces, including the bottoms of clapboards/shingles. Brush with the grain of the wood - shingles, brush up and down, clapboard - side to side. IMO, it's easiest to do the trim first, then go back and get the siding. Work left to right on each wall, top to bottom, and try not to stop with a wall partially complete - maintaining a "wet edge" (meaning you are applying new paint adjacent to an area where the paint is not yet dry) as you go.
Buy a brush cleaner (spinning tool with a handle) - these things are worth their money because they will allow you to properly clean your brushes for many, many more uses than would be possible otherwise and rinse in a five gallon bucket. Getting the most out of your brushes will save you a lot of trouble.
When you're done, put your downspouts and shutters back, and you're good to go. Recommend you get a friend to help with putting shutters back, as this can be tricky with one person. Latex paint can be disposed of down any non-storm water drain (meaning it goes to somewhere it is treated). Toilets are good for this. And since it's already diluted in water, it won't clog your pipes.
Equipment:
-Drop cloth(s) - don't get poly sheeting unless you have lead and are DIYing (in which case you also need a respirator and vacuum with HEPA filter, among other things), otherwise, cloth is good
-Brushes - size depends on what kind of siding you have, but a 2" and a 4" brush are typically must haves
-5 gallon buckets. At least 2 of them
-5-in-1 tool. Can be used as a scraper, also to open paint cans easily
-Rubber mallet. To close paint cans
-Ergonomic Hand scraper - thank me later. Just don't use uneven hand pressure (ie favor one edge over the other) or you'll gouge your wood
-Small hand pump sprayer
-Bleach
-TSP or TSP substitute
-Primer and finish coat
-Caulk
-Caulk gun
-Window glaze and putty knife (if needed)
-Brush cleaner
-24 foot fiberglass extension ladder
-6 foot fiberglass stepladder
-Screwdrivers (for removing and putting back downspouts/shutters...it's easiest with an electric)
-Small paint cans, ladder hooks if you want to go hands free from buckets when working up there.
-Deck stain (if needed)