ML 320 not starting and pouring out gas when trying to start it

It was fine for the longest time . I bought it and haven't driven it yet and a month later I go to start it and it starts pouring out gas from the back side where the gas tank is when ever I try to start it. Car doesn't turn on only cranks. It doesn't stop pouring until I stop turning the key. And only pours when I try to turn it on. I have no clue where it's coming from and I can't take t to a mechanic cause it doesn't start. The cars pretty old year 2000. Not really worth putting money in to fix but I need to sell it or use it to get to school. Any ideas what can cause this and how I can get it fixed. Got a couple mechanics willing to come look at it but I'm not sure if it's going to cost a a lot or not. I'd rather sell as is to some one who knows how to fix it for less then what I was intending on asking for .
Any ideas could help greatly.

Sounds like a fuel line is broken or disconnected.

Sounds like a fuel line is broken or disconnected.

Is this a expensive fix?