I think being UTTERLY alone (no friends or anything) is probably the greatest and most common fear. But I also think that if you surround yourself with people or even go to places where there are people you don't know you can alleviate that fear. If you are not that picky about who you are kind to, you will be surprised how many friends you can make. EVERYBODY wants to know that there is someone who cares for them.
I do remember having money concerns like cmon and rugger mention. I put myself through college working a lot which made it hard sometimes while having phone, car, etc expenses but managed to never stay more than $1000.00 in debt.
When I moved away from my parents after finishing school and started my first big corporate job, I was paranoid about messing up and losing my job. One thing that helped was a sort of meditation that I would do where I would lose my job, my car, my place, until there was nothing left but ME. When I sat with that fear and stress in my mind, I found my fear sort of melting away as I detached myself from my possessions.
I had that job 12 years and then got laid off. I had some severance pay but was in the middle of remodeling my house so I was stressed to finish with my savings. To make matters worse I was about to move here to San Diego and look for a Job. So I put my house up for sale as I saw my savings disappear, and moved with nothing but a car full of stuff and my dog, and a lot of memories of my first house and the place where I came out. I was a little worried about how long it would take to find a new job and the the housing market was in a slump. At some point, my family and friends let me know that they would help if I needed it. I realized that in my old fear I left them out of the equation and felt less stressed about everything. I had finally come to the realization of my meditation standing by a road next to a gas station in the middle of nowhere (actually west texas) with just myself, my dog and whatever I could carry. There was a strange peace an contentment being liberated from so much "stuff".
My house finally sold after 8 months at a pretty nice profit. I had actually found a job before that so I could have kept the house, but I decided I needed my liberation more. Really, if you think about it the fear of being alone and being broke have a common notion of helplessness and loss of control. Never forget there is a world of people willing to help you, and you are never completely broke if you have yourself and your friends. But also have confidence that if you don't panic and don't get overwhelmed by your fears you are capable of great things!