Some electric bass guitars have more strings, but an upright bass traditionally has 4.

eBay has many electric upright basses for sale. Another good place to purchase an electric upright bass is from a music store like Gibson Custom Shop or Dave's Guitar Shop.

Well, for one, string bass strings are a lot longer than electric bass strings. I wouldn't recommend putting string bass strings on an electric bass and vice versa.

It depends what you mean... i know what you mean by electric bass but what do you mean by "Bass" If you mean an upright bass/double bass like this

http://shannonspositiveimages.com/images/UprightBass.jpg

then with a few minor adjustments with the way you play you can.. To play an upright bass you need to use your hands all the time instead of a pick.. so finger picking is a NEED. Watch some youtube videos..

I would say an upright bass (not electric)