Step 1: Find a house to sit.
There are two ways to accomplish this: the legal way, and the illegal way. The illegal way is where you break into a house when nobody's there (preferably when they're gone on an extended vacation) and make yourself at home while watching their possessions. The legal way is where you find somebody who is legitimately trying to find a person to care for their property while they are away on an extended vacation or to care for a dying relative (hint, hint!). The legal way is preferable in this instance solely for the fact that your chances of being arrested drop considerably when you have been personally hired by a homeowner to watch over his residence.
In order to find a legitimate house sitting job you should check out the local newspaper or Craig's List (swingers, druggies, and all-around freaks of nature need people to house sit for them too). Look for ads requesting a house sitter who's a trustworthy individual who respects the property of others, and who takes his shoes off while entering a person's house. These people are usually the most desperate and the easiest to dupe into hiring you. Show up to your interview in nice clothes (but don't try to over impress with a suit and tie — they'll see right through that bullshit), smile a lot (but do not show your overenthusiastic "Joker" grin), and constantly assure the homeowner that your apartment is spotless and in perfect condition thanks to you washing the floors and dusting twice a day.
Compliment the homeowner on a lovely house, and claim that someday you wish that you could have a house "just as lovely. In fact, EXACTLY like this one." Do not snicker or laugh maniacally at this point or you may give away Step 5.
Try your best to get the homeowners to not only leave you the keys to their house, but also try to impress upon them the importance of leaving you their BMW and their 18 year-old daughter (the ease of which to do this is directly proportional to if you found the ad for the job on Craig's List, and if the owners thought that the site was a meeting place for nice Christian souls).
Shove the owners out of the house (after attaining their keys), lock the door behind them, and congratulations! You have now found yourself to officially be a house sitting fool!
Oh, and on a side note, take the time to befriend a notary public. Trust me, this is important for future steps.
Step 2: Confiscate any important credit or banking materials for the owner's own good
The first thing you should do after locking the door is to search all drawers and nightstands for credit cards or banking information in order to keep this information safe from degenerate hooligans. They are everywhere.
The best way to make sure that a credit card or savings account has not been compromised is to test them yourself; you are the only person you can trust. Call up Papa John's and see if the credit card can handle an order of 12 pizzas. Then go to Amazon.com and see if you can make at least $1,000 worth of purchases with the card. If it's okay with those numbers it should be fine and not exposed to the criminal underworld yet... Just in case though, you might want to order 2 strippers and 3 kegs from Kitty Katz Snatch down the street. Ask for Jimmy, he'll cut you a deal. If this is too much for you to handle alone it would be advisable to invite some friends over to your newly responsible-for residence in order to help you assure both yourself and those whose faith was put in your hands that you have everything under control.
Step 3: Assure neighbors and potential burglars that the house is indeed occupied
The entire point of house sitting for somebody is to keep the premises safe and secure, and not to allow any unwanted attention to fall on an empty residence. The best way to achieve this is to throw parties in the sitted house every night that you are there. The pizza, kegs, and strippers from Step 2 should keep any kind of party/parties going for at least 2 days. For the house's own security, you may be required to purchase further sustenance and titties depending on how long your sitting duties last.
The best defended houses are those that produce a lot of noise and have a lot of people in them. Nobody would want to burgle a house that had 200 people dancing, drinking, puking, and fucking all around and within it. That's common sense. Though it might be a good idea to hide all the owner's jewelry and proofs of stock purchases in your own safety deposit box for their own protection. Do a keg stand to celebrate your forward thinking. Then fuck a brunette in the master bedroom. Use the home owner's condoms in order to make yourself feel like the protector and master of this domain. If the urge hits you, sacrifice the owner's yappy lap dog to Satan in order to receive her blessing on a job well done. Bathe in the dog's blood with Jennifer, the slutty brunette.
Step 4: Defend your actions to neighbors, the police
Yes, it's true, burglars may not be the only threat trying to keep you from properly doing your job; you may get calls and visits from the owner's neighbors or the local police (both who feel threatened and insulted that the home owner did not ask them to house sit in their absence). Do not get angry at these interruptions; these people are just too shallow and childish to handle the awesome responsibilities that you have earned.
In order to show your maturity to any nosey neighbors or misguided police officers, always answer the door naked in order to inspire awe and dominance (make sure you're partly chubbed up prior to this). Most of the time this will chase away any wussy busybodies who don't belong on your land... I mean your employer's land. If your intruders do leave right away bellow out some maniacal laughter with the door still open to scare them into never coming back.
If your initial presence does not drive your visitor away at first glance, try bellowing out some maniacal laughter. If that does not work ask if there is a problem. They might claim something about "noise ordinances," or "streakers in the neighborhood usually running from" your house, or some such other nonsense that is basically just shrouded jealousy that they did not get invited to your anti-burglary party. Don't let them bring you down. Urinate on them in order to show them how pitiful they really are. If you urinate on a police officer and he starts to take out his handcuffs you must immediately produce an attractive (preferably naked) woman and offer her services to the pig if he would simply report that all was well with your housely responsibilities. If he still insists on handcuffing you throw the naked woman at him to distract him, then get behind him and snap his neck. Bury the body in the basement or set it on fire on the front porch of the nosey neighbor who called the cops in the first place. You must show them that their actions have equal and opposite reactions... That's physics.
Step 5: Recognize that this house is too good for its owners. It should be YOURS
You know what you have to do: wait for the home owners to come home and kill them. Quickly and painlessly would be best; they probably don't even know what they did wrong. They're simpletons. A bullet in the back of their heads would be nicest. If they have an 18 year-old (or older) daughter who they did not originally leave in your care, you can make her yours if you so wish. She needs to know what a REAL man feels like. If they have a daughter who's younger than 18... Well, check the state laws, it may still be okay. Though even if it isn't "legal", she's never leaving the house again anyway, so just fuck the law.
Write out a last will and testament and sign it with the same signature that you found on all those legal documents in the safe in the master bedroom closet. Pass everything over to yourself in the will. Have your new notary friend sign and seal it as a legitimate document. Urinate on the document to prove that you are now the alpha male of the house.
Then make out a suicide note in the owner's handwriting. In the letter you should claim that "[your] wife was a bitch, [your] son was gay, and [you] cannot go on living a lie!" End the letter without being specific as to what lie you are referring to. This will keep the authorities guessing and off your case. Then riddle the bodies with bullets, put them all in their little Honda Accord, set the car on fire and then roll it down a big hill (preferably into a gas station or something just as equally flammable/combustible).
Step 6: NEVER leave your house in the hands of anybody else
Seriously, there are a lot of sick fucks out there. They cannot be trusted.
If you now own a luscious and most non-heinous house of your own without ever having to sign a mortgage, then congratulations! You've successfully house sat!
Solutions to problems that might arise:
Q: What do I do if I throw a party at the house that I'm sitting, but I can't get it up for the strippers and whores that I invited over?
A: Coke. Do lots of coke.
Q: What if it turns out that the house I'm sitting is kind of shitty, and I don't like it?
A: Who gives a shit? Free house!
Q: What if the SWAT Team arrives, and I don't have enough naked girls to go around?
A: First, get the entire party drunk or drugged out of their minds. Then, set up at least nine large propane tanks in strategic locations around the house and open them up to leak as fast as they can. You should then exit via the back door or through a secret tunnel you had previously dug from the basement into the neighbor's yard. Before you dive into the secret tunnel though, program the microwave to start up when you call the house number, and have the microwave start on "high" with 4 cans of hairspray in it. If all goes well the entire SWAT team should all rush into the house just when the cans ignite in a fireball, thusly causing all the propane to explode in a blast that should be strong enough to be seen from the International Space Station. Exit your tunnel, go back to your old apartment and check out the paper or Craig's List to see if anybody else is looking for a house sitter.