Here are a few reasons why you do not want to move in with a friend and some personal experiences from when I lived with my 2 best friends.
Personal Space and Quiet time:
When living with friends you will not have any privacy or quiet time, and the closer the friends you are the worse it will be. You may not realize it now but you are not always in the mood to be with your friends sometimes you may want to just sit in your room and relax, and if a friend called you up you could say you were busy but if you live with a friend they will be knocking on the door and bothering you all the time, and good friends will often borrow things of yours without asking you. Where as someone you found online will usually leave you alone when your door is closed except for something important.
My old roommate would always go into my room to borrow my things no matter how much I asked her not to, and every time I asked she would get insulted because it was her so it should be ok with me.
The reason why you moved in to an apartment is because you needed help being able to afford your expenses, and someone you dont know will usually be more responsible with making sure they have the money to bay their half of the bills then a friend will, a friend will ask you to help them out when they are short on cash.
One of my friends would always spend his rent or bill money in online casinos playing blackjack, or in poker rooms online. I like to play some poker online just as much as anyone else but I always made sure to not gamble in an online casino with my rent money. If I was short on money I would not gamble, but I would never allow myself to not have the money to pay my share of the bills.
Cleaning of the Shared Spaces:
In the past roommates I had found in the news paper always made sure that any space we shared like the kitchen or living room was kept clean. If you cooked something any mess was cleaned from the counter and pots, pans and plates would be put in the sink and were taken care of within 12 hours, but friends may take advantage of the slack you will give to a friend, because they know you would be ok with it.
One friend of mine hated anything being left in the sink for any amount of time and if it was left fore more then an hr or 2 she would complain, so me and my other roommate started cleaning the dishes as soon as we were done with them, only to find that she would leave her dishes sometimes for days and when questioned about it she said that her seeing our dishes bothered her but her dishes did not bother her so it was ok for her to leave them.
Unless your roommate has lots of money and lets face it if they had cash they would not need a roommate, then they will be looking to save money and not want to waste money on electricity, and once you agree on things like using the dryer or air conditioning two roommates who meet online or from an add in the paper will usually respect the rules better then two friends will. Friends will usually bend the rules, like leaving the computer on all day or running the ac all night.
My friends used to leave their Air conditionings on all day long and would often leave their rooms and even the apartment without turning them off, and instead of being more responsible for their actions they would make up excuses like “oops I forgot”.
These are just some of the many reasons you should avoid living with friends, especially if you want to keep them as friends. It is one thing if a friend needs a place to stay for a week or two but never ever let them move in.