1. Airless. Shouldn't cost you $2000. I see a Titan Xi345 on Lowes.com for $80 and LX60 gun for $50. You need a hose. All-in-one Wagner kit is $295 with hose and cart. The titan's better than the Wagner. The problem though is that the sprayers that weak aren't really good for more than primer. Which is why I say...
2. Rent, if you can, a pro rig designed for 5 gal buckets. Some places won't rent to you because they get screwed all the time by people not cleaning them. Alternately, buy it and resell it minus what it would've cost for you to rent it, about $100/day.
3. Depends on how they finished it. If they finished it to a grade 2 and textured, PVA primer and color coat. If they finished it to grade 3 and smooth, you'll want PVA, a really thick hide primer, and then a decently thick color coat.
4. Commercial account with Sherwin Williams. They'll help you estimate.
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Cautions:
-- You'll want to mask like you cannot believe. It'll take you, as someone who is not experienced with it, much longer to mask than it will take you to roll the house. I honestly wouldn't spray the inside because of the masking 'overhead'. I'd just roll it and move on. Don't rent the sprayer if you're renting until you've finished masking. You'll also spend more time fixing spray-throughs, boogers, and drips than you would if you'd just rolled in the first place.
-- Unless you're spraying paint or primer that was mixed at the paint store a few hours before, use a strainer. Nothing will ruin your productivity like stopping to fix lumps in the paint and having the latex gum up in the tip.
-- Make sure you know how to test viscosity (viscosity cup) and that you can get the appropriate tips for the viscosity of paint that you're using. Otherwise... thar be drips.
-- Keep a roller handy to fix the drips you're going to get anyway because you're a n00b.
-- You need a rolling scaffolding to get close enough to the wall. Plan to rent that too or buy it. No, with a sprayer you can NOT get by with a ladder or three.
Last but not least, for the grace God gave little green apples, use real paint and not builder grade sheet. The builder grade sheet is easier to spray but will wipe right off the damned wall the first time a dog or a rug rat bumps into it. Use flat on the ceiling, eggshell on the walls so that it'll wipe clean, and honest-to-god-actual-cleans-up-with-mineral-spirits oil/enamel on the doorframes and trim so it won't stick.
[This message has been edited by superspeck (edited 1/12/2013 1:57p).]