How much would it cost to open up a gas station business? -

A gas station costs between $500,000 to about $4,000,000 depending on location and volume.

If you go into Bankruptcy, as individual, can you start your own business later on, or there are restrictions? -

You will not be able to obtain credit for your LLC, but you can certainly start one.

There are no restrictions - however, its a great leap of faith that somebody would be successful in their own business down the line from personal bankruptcy. Your credit profile would show a BK, but you needn t use your name or SSN for a new venture.

http://diylegalinfo.com/bankruptcy_Links.html has a lot of information on bankruptcy questions, how to handle them yourself and other information.